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 (
    4, 1, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 
    17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 
    27, 28, 29, 30, 31, 32, 33, 34, 35
  ) 
  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 0.00097

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "117.98"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "64.00"
      },
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "ALL",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "rows_examined_per_scan": 254,
        "rows_produced_per_join": 63,
        "filtered": "25.20",
        "cost_info": {
          "read_cost": "41.18",
          "eval_cost": "12.80",
          "prefix_cost": "53.98",
          "data_read_per_join": "1K"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`pankajecarter_systemfour`.`cscart_product_prices`.`lower_limit` = 1) and (`pankajecarter_systemfour`.`cscart_product_prices`.`product_id` in (4,1,5,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35)) and (`pankajecarter_systemfour`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}