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 (
    9982, 9923, 21325, 32298, 10997, 32872, 
    21326, 31794, 32348, 11084, 11049, 
    11073, 32345, 13201, 32341, 13255, 
    13203, 13218, 13200, 32333, 33025, 
    13229, 33810, 13195, 33014, 6615, 13205, 
    33157, 18220, 18205, 18198, 18197, 
    18216, 11080, 18210, 60881, 18219, 
    18222, 18212, 18196, 18217, 33000, 
    18202, 18206, 18224, 18208, 18201, 
    36477, 18203, 18213
  ) 
  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 0.00144

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "35.01"
    },
    "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": 50,
        "rows_produced_per_join": 9,
        "filtered": "20.00",
        "index_condition": "(`cscartdb`.`cscart_product_prices`.`product_id` in (9982,9923,21325,32298,10997,32872,21326,31794,32348,11084,11049,11073,32345,13201,32341,13255,13203,13218,13200,32333,33025,13229,33810,13195,33014,6615,13205,33157,18220,18205,18198,18197,18216,11080,18210,60881,18219,18222,18212,18196,18217,33000,18202,18206,18224,18208,18201,36477,18203,18213))",
        "cost_info": {
          "read_cost": "34.01",
          "eval_cost": "1.00",
          "prefix_cost": "35.01",
          "data_read_per_join": "239"
        },
        "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)))"
      }
    }
  }
}