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 (
    8145, 8202, 8322, 8306, 8235, 8247, 8250, 
    8238, 8338, 8259, 8149, 8200, 8324, 
    8323, 8325, 8326, 8327, 8328, 8337, 
    8150, 8142, 8151, 8134, 8140, 8122, 
    8127, 8132, 8167, 7885, 8130, 9313, 
    8139, 8143, 8152, 8411, 9291
  ) 
  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 0.00122

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "25.21"
    },
    "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": 36,
        "rows_produced_per_join": 7,
        "filtered": "19.99",
        "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`product_id` in (8145,8202,8322,8306,8235,8247,8250,8238,8338,8259,8149,8200,8324,8323,8325,8326,8327,8328,8337,8150,8142,8151,8134,8140,8122,8127,8132,8167,7885,8130,9313,8139,8143,8152,8411,9291))",
        "cost_info": {
          "read_cost": "24.49",
          "eval_cost": "0.72",
          "prefix_cost": "25.21",
          "data_read_per_join": "172"
        },
        "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)))"
      }
    }
  }
}