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 (
    50216, 50194, 41341, 41340, 47922, 47921, 
    41343, 47896, 47924, 47923, 31632, 
    31634, 31631, 41339, 2303, 31627, 31965, 
    26880, 26895, 26894, 26876, 26885, 
    26881, 26884, 26883, 31629, 41397, 
    1972, 31630, 3764, 36746, 2085
  ) 
  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 0.00693

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": 32,
          "filtered": 99.9960556,
          "index_condition": "cscart_product_prices.product_id in (50216,50194,41341,41340,47922,47921,41343,47896,47924,47923,31632,31634,31631,41339,2303,31627,31965,26880,26895,26894,26876,26885,26881,26884,26883,31629,41397,1972,31630,3764,36746,2085)",
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}