SELECT 
  cscart_ult_product_prices.product_id, 
  MIN(
    IF(
      cscart_ult_product_prices.percentage_discount = 0, 
      cscart_ult_product_prices.price, 
      cscart_ult_product_prices.price - (
        cscart_ult_product_prices.price * cscart_ult_product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  cscart_ult_product_prices 
WHERE 
  cscart_ult_product_prices.product_id IN (
    4718, 4793, 4774, 4776, 4078, 4779, 4777, 
    4792, 4787, 4858, 4786, 4790, 4778, 
    4856, 4860, 4796, 4797, 4795, 4794, 
    4857, 5006, 4878, 4112, 4110
  ) 
  AND cscart_ult_product_prices.lower_limit = 1 
  AND cscart_ult_product_prices.company_id = 1 
  AND cscart_ult_product_prices.usergroup_id IN (0, 0, 1) 
GROUP BY 
  cscart_ult_product_prices.product_id

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "cscart_ult_product_prices.product_id",
      "temporary_table": {
        "table": {
          "table_name": "cscart_ult_product_prices",
          "access_type": "ALL",
          "possible_keys": [
            "usergroup",
            "product_id",
            "company_id",
            "lower_limit",
            "usergroup_id"
          ],
          "rows": 44,
          "filtered": 56.81818008,
          "attached_condition": "cscart_ult_product_prices.lower_limit = 1 and cscart_ult_product_prices.company_id = 1 and cscart_ult_product_prices.product_id in (4718,4793,4774,4776,4078,4779,4777,4792,4787,4858,4786,4790,4778,4856,4860,4796,4797,4795,4794,4857,5006,4878,4112,4110) and cscart_ult_product_prices.usergroup_id in (0,0,1)"
        }
      }
    }
  }
}