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 (
    2598, 6187, 6188, 6189, 6190, 2730, 2731, 
    2732, 2733, 2734, 6318, 6319, 6320, 
    6321, 2726, 2727, 2728, 2729, 6313, 
    6314, 6315, 6316, 6317, 1573, 1574, 
    1575, 1576, 1577, 1578, 1579, 1580, 
    1581, 1582, 1583, 1584, 1585, 1586, 
    1587, 1588, 1589, 1590, 1591, 1592, 
    1593, 1594, 1595, 1596, 1597, 1598, 
    5272, 5273, 5274, 5275, 5276, 5277, 
    5278, 5279, 5280, 5281, 5282, 5283, 
    5284, 5285, 5286, 5287, 5288, 5289, 
    5290, 5291, 5292, 5293, 5294, 5295, 
    5296, 5297, 5298, 1546, 1547, 1548, 
    1549, 1550, 1551, 1552, 1553, 1554, 
    1555, 1556, 1557, 1558, 1559, 1560, 
    1561, 1562, 1563, 1564, 1565
  ) 
  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 0.00198

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "67.21"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "range",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "key": "product_id",
        "used_key_parts": [
          "product_id"
        ],
        "key_length": "3",
        "rows_examined_per_scan": 96,
        "rows_produced_per_join": 19,
        "filtered": "20.00",
        "index_condition": "(`gaseus`.`cscart_product_prices`.`product_id` in (2598,6187,6188,6189,6190,2730,2731,2732,2733,2734,6318,6319,6320,6321,2726,2727,2728,2729,6313,6314,6315,6316,6317,1573,1574,1575,1576,1577,1578,1579,1580,1581,1582,1583,1584,1585,1586,1587,1588,1589,1590,1591,1592,1593,1594,1595,1596,1597,1598,5272,5273,5274,5275,5276,5277,5278,5279,5280,5281,5282,5283,5284,5285,5286,5287,5288,5289,5290,5291,5292,5293,5294,5295,5296,5297,5298,1546,1547,1548,1549,1550,1551,1552,1553,1554,1555,1556,1557,1558,1559,1560,1561,1562,1563,1564,1565))",
        "cost_info": {
          "read_cost": "65.29",
          "eval_cost": "1.92",
          "prefix_cost": "67.21",
          "data_read_per_join": "460"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`gaseus`.`cscart_product_prices`.`lower_limit` = 1) and (`gaseus`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}