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 (
    1302527, 1444123, 1903007, 1302528, 
    1903046, 1439066, 1903044, 1439065, 
    1903053, 1444124, 1903049, 1903047, 
    1903051, 1927850, 1927856, 1927849, 
    1927858, 1927857, 1942053, 2382472, 
    2382440, 2382470, 2382443, 2382442
  ) 
  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 0.00197

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "56.27"
    },
    "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": "51.48",
          "eval_cost": "4.80",
          "prefix_cost": "56.28",
          "data_read_per_join": "1K"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`maniamall_cscart`.`cscart_product_prices`.`lower_limit` = 1) and (`maniamall_cscart`.`cscart_product_prices`.`product_id` in (1302527,1444123,1903007,1302528,1903046,1439066,1903044,1439065,1903053,1444124,1903049,1903047,1903051,1927850,1927856,1927849,1927858,1927857,1942053,2382472,2382440,2382470,2382443,2382442)) and (`maniamall_cscart`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}

Result