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 (
    13860, 13876, 13879, 14024, 13896, 13946, 
    13916, 13963, 13919, 13929, 13932, 
    13895, 14020, 13899, 13861, 13971, 
    13902, 13931, 13939, 13913, 14026, 
    13950, 13940, 13947
  ) 
  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 0.00214

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.061901304,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_prices",
          "access_type": "range",
          "possible_keys": [
            "usergroup",
            "product_id",
            "lower_limit",
            "usergroup_id"
          ],
          "key": "usergroup",
          "key_length": "9",
          "used_key_parts": ["product_id", "usergroup_id", "lower_limit"],
          "loops": 1,
          "rows": 48,
          "cost": 0.04656984,
          "filtered": 49.95579147,
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.product_id in (13860,13876,13879,14024,13896,13946,13916,13963,13919,13929,13932,13895,14020,13899,13861,13971,13902,13931,13939,13913,14026,13950,13940,13947) and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}