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 (
    32019, 9933, 12034, 12033, 9918, 27758, 
    69929, 38318, 35227, 34334, 38426, 
    31951, 34347, 34575, 7471, 32137, 35450, 
    32240, 38330, 38352, 39033, 35352, 
    7523, 37523, 35334, 7476, 7420, 35966, 
    32011, 32218, 35691, 32200, 35735, 
    70305, 71343, 71347, 71884, 72167, 
    72174
  ) 
  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 0.00128

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "27.76"
    },
    "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": 40,
        "rows_produced_per_join": 7,
        "filtered": "20.00",
        "index_condition": "(`cscartdb`.`cscart_product_prices`.`product_id` in (32019,9933,12034,12033,9918,27758,69929,38318,35227,34334,38426,31951,34347,34575,7471,32137,35450,32240,38330,38352,39033,35352,7523,37523,35334,7476,7420,35966,32011,32218,35691,32200,35735,70305,71343,71347,71884,72167,72174))",
        "cost_info": {
          "read_cost": "26.96",
          "eval_cost": "0.80",
          "prefix_cost": "27.76",
          "data_read_per_join": "191"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`cscartdb`.`cscart_product_prices`.`lower_limit` = 1) and (`cscartdb`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}