SELECT 
  cscart_product_prices.product_id, 
  MIN(
    IF(
      cscart_product_prices.percentage_discount = 0, 
      cscart_product_prices.price, 
      cscart_product_prices.price - (
        cscart_product_prices.price * cscart_product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  cscart_product_prices 
WHERE 
  cscart_product_prices.product_id IN (
    19134, 
    19300, 
    19139, 
    19079, 
    19151, 
    19294, 
    18489, 
    19220, 
    19187, 
    19069, 
    18910, 
    19203, 
    18825, 
    18997, 
    19254, 
    19233, 
    19102, 
    18896, 
    19065, 
    18840, 
    18638, 
    19105, 
    18995, 
    18506, 
    18660, 
    18845, 
    18882, 
    19111, 
    19330, 
    18835, 
    19373, 
    18990, 
    18570, 
    18643, 
    18634, 
    18960, 
    19342, 
    19214, 
    18899, 
    19189, 
    18942, 
    19175, 
    18967, 
    19211, 
    19033, 
    19040, 
    18587, 
    18876, 
    18696, 
    19185, 
    19083, 
    18936, 
    18934, 
    18781, 
    18832, 
    19397, 
    19341, 
    19382, 
    19252, 
    19277, 
    19331, 
    19086, 
    19171, 
    19167, 
    18888, 
    19030, 
    19399, 
    18972, 
    19113, 
    19328, 
    19148, 
    19289, 
    19060, 
    18984, 
    18938, 
    19353, 
    19346, 
    18884, 
    19183, 
    19094, 
    19325, 
    18564, 
    19169, 
    18518, 
    19351, 
    18779, 
    18850, 
    19058, 
    18861, 
    19359, 
    19292, 
    19261, 
    19141, 
    18805, 
    18951, 
    19074, 
    19302, 
    18599, 
    19027, 
    18836, 
    19315, 
    18787, 
    19024, 
    18798, 
    19244, 
    18903, 
    19192, 
    19032, 
    19072, 
    19303, 
    19051, 
    19163, 
    18962, 
    18878, 
    18911, 
    19082, 
    19298, 
    19339, 
    19223, 
    19275, 
    18855, 
    18496, 
    18565, 
    18793, 
    18954, 
    19020, 
    18927, 
    18958, 
    19055, 
    18843, 
    18906, 
    19123, 
    19311, 
    19119, 
    19200, 
    18947, 
    18588, 
    19372, 
    18821, 
    18873, 
    19198, 
    18875, 
    19272, 
    19168, 
    18823, 
    18901, 
    18555, 
    19129, 
    19202, 
    18837, 
    18956, 
    18886, 
    18905, 
    18869, 
    19282, 
    19159, 
    19264, 
    18671, 
    19237, 
    19259, 
    19251, 
    18512, 
    19078, 
    19047, 
    19266, 
    18999, 
    18784, 
    18790, 
    18930, 
    19310, 
    18913, 
    18791, 
    18894, 
    18914, 
    18964, 
    18918, 
    18827, 
    19242, 
    18987, 
    19004
  ) 
  AND cscart_product_prices.lower_limit = 1 
  AND cscart_product_prices.usergroup_id IN (0, 1) 
GROUP BY 
  cscart_product_prices.product_id

Query time 0.00240

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "126.01"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "range",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "key": "product_id",
        "used_key_parts": [
          "product_id"
        ],
        "key_length": "3",
        "rows_examined_per_scan": 180,
        "rows_produced_per_join": 35,
        "filtered": "20.00",
        "index_condition": "(`chocoramo`.`cscart_product_prices`.`product_id` in (19134,19300,19139,19079,19151,19294,18489,19220,19187,19069,18910,19203,18825,18997,19254,19233,19102,18896,19065,18840,18638,19105,18995,18506,18660,18845,18882,19111,19330,18835,19373,18990,18570,18643,18634,18960,19342,19214,18899,19189,18942,19175,18967,19211,19033,19040,18587,18876,18696,19185,19083,18936,18934,18781,18832,19397,19341,19382,19252,19277,19331,19086,19171,19167,18888,19030,19399,18972,19113,19328,19148,19289,19060,18984,18938,19353,19346,18884,19183,19094,19325,18564,19169,18518,19351,18779,18850,19058,18861,19359,19292,19261,19141,18805,18951,19074,19302,18599,19027,18836,19315,18787,19024,18798,19244,18903,19192,19032,19072,19303,19051,19163,18962,18878,18911,19082,19298,19339,19223,19275,18855,18496,18565,18793,18954,19020,18927,18958,19055,18843,18906,19123,19311,19119,19200,18947,18588,19372,18821,18873,19198,18875,19272,19168,18823,18901,18555,19129,19202,18837,18956,18886,18905,18869,19282,19159,19264,18671,19237,19259,19251,18512,19078,19047,19266,18999,18784,18790,18930,19310,18913,18791,18894,18914,18964,18918,18827,19242,18987,19004))",
        "cost_info": {
          "read_cost": "122.41",
          "eval_cost": "3.60",
          "prefix_cost": "126.01",
          "data_read_per_join": "863"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`chocoramo`.`cscart_product_prices`.`lower_limit` = 1) and (`chocoramo`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}

Result

product_id price
18489 26.40000000
18496 28.40000000
18506 26.40000000
18512 48.00000000
18518 28.40000000
18555 28.40000000
18564 28.40000000
18565 22.40000000
18570 58.40000000
18587 23.40000000
18588 72.40000000
18599 28.40000000
18634 29.40000000
18638 26.40000000
18643 58.40000000
18660 26.40000000
18671 72.40000000
18696 58.40000000
18779 28.40000000
18781 28.40000000
18784 66.80000000
18787 28.40000000
18790 28.40000000
18791 21.40000000
18793 45.40000000
18798 45.40000000
18805 39.40000000
18821 34.40000000
18823 44.40000000
18825 26.40000000
18827 33.40000000
18832 44.40000000
18835 23.40000000
18836 33.40000000
18837 28.40000000
18840 26.40000000
18843 42.00000000
18845 72.40000000
18850 45.40000000
18855 22.40000000
18861 58.40000000
18869 34.40000000
18873 44.40000000
18875 44.40000000
18876 28.40000000
18878 49.40000000
18882 39.40000000
18884 28.40000000
18886 50.40000000
18888 44.40000000
18894 45.40000000
18896 50.40000000
18899 44.40000000
18901 37.00000000
18903 28.40000000
18905 31.40000000
18906 49.40000000
18910 44.40000000
18911 31.40000000
18913 28.40000000
18914 22.40000000
18918 22.40000000
18927 74.00000000
18930 22.40000000
18934 29.40000000
18936 50.40000000
18938 33.40000000
18942 51.40000000
18947 71.00000000
18951 37.00000000
18954 27.00000000
18956 22.40000000
18958 37.00000000
18960 32.00000000
18962 52.00000000
18964 74.00000000
18967 51.40000000
18972 45.40000000
18984 30.00000000
18987 45.40000000
18990 45.40000000
18995 26.40000000
18997 72.40000000
18999 28.40000000
19004 26.40000000
19020 39.40000000
19024 42.40000000
19027 44.40000000
19030 44.40000000
19032 51.40000000
19033 23.40000000
19040 39.40000000
19047 57.00000000
19051 45.40000000
19055 39.40000000
19058 22.00000000
19060 28.40000000
19065 26.40000000
19069 28.40000000
19072 27.40000000
19074 39.40000000
19078 26.40000000
19079 26.40000000
19082 28.40000000
19083 23.40000000
19086 34.40000000
19094 49.40000000
19102 28.40000000
19105 26.40000000
19111 39.40000000
19113 44.40000000
19119 79.20000000
19123 28.40000000
19129 79.20000000
19134 29.40000000
19139 28.40000000
19141 72.40000000
19148 29.40000000
19151 51.40000000
19159 52.80000000
19163 49.40000000
19167 28.40000000
19168 41.40000000
19169 23.40000000
19171 51.40000000
19175 44.40000000
19183 34.40000000
19185 58.40000000
19187 79.20000000
19189 43.00000000
19192 29.40000000
19198 44.40000000
19200 19.30000000
19202 25.40000000
19203 26.40000000
19211 72.40000000
19214 49.40000000
19220 50.40000000
19223 44.40000000
19233 26.40000000
19237 34.40000000
19242 22.40000000
19244 44.40000000
19251 58.00000000
19252 45.40000000
19254 26.40000000
19259 52.80000000
19261 49.40000000
19264 28.40000000
19266 89.40000000
19272 48.00000000
19275 44.40000000
19277 44.40000000
19282 85.20000000
19289 23.40000000
19292 27.40000000
19294 44.40000000
19298 29.40000000
19300 49.40000000
19302 52.40000000
19303 28.40000000
19310 66.00000000
19311 44.40000000
19315 25.40000000
19325 28.40000000
19328 49.40000000
19330 45.40000000
19331 72.40000000
19339 34.40000000
19341 58.40000000
19342 45.40000000
19346 34.40000000
19351 43.00000000
19353 49.40000000
19359 22.00000000
19372 72.40000000
19373 72.40000000
19382 71.00000000
19397 44.40000000
19399 72.40000000