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 (
    1285, 1283, 1284, 1282, 1885, 1628, 1625, 
    1783, 1779, 1782, 1781, 1827, 1454, 
    1476, 1473, 1066, 1399, 1387, 1054, 
    1369, 1370, 1290, 1291, 1292, 1784, 
    1286, 1287, 1288, 1289
  ) 
  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 0.00127

JSON explain

{
  "query_block": {
    "select_id": 1,
    "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": 29,
      "filtered": 5.918365955,
      "index_condition": "cscart_product_prices.product_id in (1285,1283,1284,1282,1885,1628,1625,1783,1779,1782,1781,1827,1454,1476,1473,1066,1399,1387,1054,1369,1370,1290,1291,1292,1784,1286,1287,1288,1289)",
      "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
    }
  }
}