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 (
    8137, 8680, 8688, 9048, 9051, 9160, 9234, 
    9323, 9325, 9451, 9455, 9732, 9773, 
    10449, 10510, 6987, 7222, 7223, 7453, 
    7508, 7558, 7559, 7565, 7567
  ) 
  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 0.00297

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "19.06"
    },
    "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": 29,
        "rows_produced_per_join": 5,
        "filtered": "19.99",
        "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`product_id` in (8137,8680,8688,9048,9051,9160,9234,9323,9325,9451,9455,9732,9773,10449,10510,6987,7222,7223,7453,7508,7558,7559,7565,7567))",
        "cost_info": {
          "read_cost": "18.48",
          "eval_cost": "0.58",
          "prefix_cost": "19.06",
          "data_read_per_join": "139"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`lower_limit` = 1) and (`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}