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 (
    1881, 23162, 4706, 225, 2237, 2510, 3860, 
    33131, 400, 5455, 4717, 2963, 6533, 
    5835, 33133, 2910, 5421, 33134, 3786, 
    3469, 6089, 297, 14965, 46739, 46734, 
    27363, 3447, 16601, 6562, 1781, 33716, 
    3885
  ) 
  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 0.05388

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "cscart_product_prices.product_id",
      "temporary_table": {
        "nested_loop": [
          {
            "table": {
              "table_name": "cscart_product_prices",
              "access_type": "ref",
              "possible_keys": [
                "usergroup",
                "product_id",
                "lower_limit",
                "usergroup_id"
              ],
              "key": "lower_limit",
              "key_length": "3",
              "used_key_parts": ["lower_limit"],
              "ref": ["const"],
              "rows": 25327,
              "filtered": 8.080804825,
              "attached_condition": "cscart_product_prices.lower_limit <=> 1 and cscart_product_prices.product_id in (1881,23162,4706,225,2237,2510,3860,33131,400,5455,4717,2963,6533,5835,33133,2910,5421,33134,3786,3469,6089,297,14965,46739,46734,27363,3447,16601,6562,1781,33716,3885) and cscart_product_prices.usergroup_id in (0,1)"
            }
          }
        ]
      }
    }
  }
}