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 (
    1274, 1406, 1266, 1428, 1263, 1256, 1319, 
    1273, 4526, 1532, 4796, 4562, 8499, 
    8502, 8501, 4798, 1284, 1528, 4767, 
    1517, 1542, 4744, 8498, 8497, 1540, 
    1544, 4571, 4812, 1538, 8503, 8505, 
    8496, 4565, 4570, 4567, 4568, 10136, 
    10137, 4569, 5774
  ) 
  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 0.00169

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "28.01"
    },
    "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": 40,
        "rows_produced_per_join": 7,
        "filtered": "19.99",
        "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`product_id` in (1274,1406,1266,1428,1263,1256,1319,1273,4526,1532,4796,4562,8499,8502,8501,4798,1284,1528,4767,1517,1542,4744,8498,8497,1540,1544,4571,4812,1538,8503,8505,8496,4565,4570,4567,4568,10136,10137,4569,5774))",
        "cost_info": {
          "read_cost": "27.21",
          "eval_cost": "0.80",
          "prefix_cost": "28.01",
          "data_read_per_join": "191"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`lower_limit` = 1) and (`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}