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 (
    295774, 303250, 308376, 316325, 317505, 
    319376, 325547, 325710, 325715, 322000, 
    6276, 19341, 119170, 142807, 162962, 
    164053, 180420, 220516, 238478, 242500, 
    263871, 295549, 295825, 317507
  ) 
  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 0.00148

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "21.63"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "range",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "key": "usergroup",
        "used_key_parts": [
          "product_id",
          "usergroup_id",
          "lower_limit"
        ],
        "key_length": "9",
        "rows_examined_per_scan": 48,
        "rows_produced_per_join": 48,
        "filtered": "100.00",
        "cost_info": {
          "read_cost": "16.83",
          "eval_cost": "4.80",
          "prefix_cost": "21.63",
          "data_read_per_join": "1K"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`unicomps`.`cscart_product_prices`.`lower_limit` = 1) and (`unicomps`.`cscart_product_prices`.`product_id` in (295774,303250,308376,316325,317505,319376,325547,325710,325715,322000,6276,19341,119170,142807,162962,164053,180420,220516,238478,242500,263871,295549,295825,317507)) and (`unicomps`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}