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 (
    4691, 4692, 4696, 4694, 4695, 4693, 5025, 
    4302, 5019, 5026, 5020, 5027, 5024
  ) 
  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 0.00053

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "cscart_product_prices.product_id",
      "temporary_table": {
        "table": {
          "table_name": "cscart_product_prices",
          "access_type": "range",
          "possible_keys": [
            "usergroup",
            "product_id",
            "lower_limit",
            "usergroup_id"
          ],
          "key": "usergroup_id",
          "key_length": "6",
          "used_key_parts": ["usergroup_id", "product_id"],
          "rows": 26,
          "filtered": 100,
          "index_condition": "cscart_product_prices.product_id in (4691,4692,4696,4694,4695,4693,5025,4302,5019,5026,5020,5027,5024) and cscart_product_prices.usergroup_id in (0,1)",
          "attached_condition": "cscart_product_prices.lower_limit = 1"
        }
      }
    }
  }
}