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 (
    33725, 33723, 33724, 34053, 50444, 25850, 
    26657, 1054, 350, 351, 36474, 2248, 
    2247, 2251, 36307, 1050, 2252, 3988, 
    36297, 2249, 353, 33721, 2260, 41230, 
    18710, 36299, 36475, 45597, 50235, 
    50234
  ) 
  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 0.00963

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_prices",
          "access_type": "range",
          "possible_keys": [
            "usergroup",
            "product_id",
            "lower_limit",
            "usergroup_id"
          ],
          "key": "product_id",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "rows": 30,
          "filtered": 99.9960556,
          "index_condition": "cscart_product_prices.product_id in (33725,33723,33724,34053,50444,25850,26657,1054,350,351,36474,2248,2247,2251,36307,1050,2252,3988,36297,2249,353,33721,2260,41230,18710,36299,36475,45597,50235,50234)",
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}