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 (
    337, 335, 334, 329, 330, 331, 325, 319, 
    320, 321, 322, 323, 318, 317, 306, 307, 
    308, 309, 310, 311, 312, 313, 314, 315, 
    316, 303, 304, 305, 302, 301, 300, 298, 
    293, 292, 291, 290, 287, 278, 280, 282, 
    247, 248, 241, 244, 245, 246, 240, 6
  ) 
  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 0.00111

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "159.80"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "96.00"
      },
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "ALL",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "rows_examined_per_scan": 302,
        "rows_produced_per_join": 96,
        "filtered": "31.79",
        "cost_info": {
          "read_cost": "44.60",
          "eval_cost": "19.20",
          "prefix_cost": "63.80",
          "data_read_per_join": "2K"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`atulecarter_atul_demo1`.`cscart_product_prices`.`lower_limit` = 1) and (`atulecarter_atul_demo1`.`cscart_product_prices`.`product_id` in (337,335,334,329,330,331,325,319,320,321,322,323,318,317,306,307,308,309,310,311,312,313,314,315,316,303,304,305,302,301,300,298,293,292,291,290,287,278,280,282,247,248,241,244,245,246,240,6)) and (`atulecarter_atul_demo1`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}