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 (
    286, 278, 280, 282, 247, 248, 241, 244, 
    245, 246, 240, 6, 66, 166, 214, 219, 221, 
    223, 192, 194, 195, 196, 197, 198
  ) 
  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 0.00048

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "102.39"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "48.00"
      },
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "ALL",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "rows_examined_per_scan": 256,
        "rows_produced_per_join": 48,
        "filtered": "18.75",
        "cost_info": {
          "read_cost": "44.79",
          "eval_cost": "9.60",
          "prefix_cost": "54.39",
          "data_read_per_join": "1K"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`atulecarter_new_april_setup`.`cscart_product_prices`.`lower_limit` = 1) and (`atulecarter_new_april_setup`.`cscart_product_prices`.`product_id` in (286,278,280,282,247,248,241,244,245,246,240,6,66,166,214,219,221,223,192,194,195,196,197,198)) and (`atulecarter_new_april_setup`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}