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 (
    630, 3866, 3867, 3568, 3868, 3567, 3869, 
    3870, 3872, 3517, 3516, 3518, 3871, 
    3570, 3569, 3876, 37850, 3577, 1400, 
    3862, 3519, 1401, 3863, 1409, 3578, 
    3864, 3861, 35731, 23261, 1399, 632, 
    3021
  ) 
  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 0.00195

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 (630,3866,3867,3568,3868,3567,3869,3870,3872,3517,3516,3518,3871,3570,3569,3876,37850,3577,1400,3862,3519,1401,3863,1409,3578,3864,3861,35731,23261,1399,632,3021)",
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}