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 (
    280, 282, 278, 20, 119, 100, 46, 204, 45, 
    68, 29, 6, 8, 14, 9, 10, 19, 21, 7, 27, 124, 
    50, 51, 49, 48, 54, 44, 194, 137, 153, 
    164, 236, 234, 150, 151, 178, 181, 248, 
    65, 64, 63, 62, 66, 140, 141, 144, 143, 
    142, 13
  ) 
  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 0.00071

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "153.65"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "98.00"
      },
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "ALL",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "rows_examined_per_scan": 262,
        "rows_produced_per_join": 97,
        "filtered": "37.40",
        "cost_info": {
          "read_cost": "36.05",
          "eval_cost": "19.60",
          "prefix_cost": "55.65",
          "data_read_per_join": "2K"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`danishecarter_25_march`.`cscart_product_prices`.`lower_limit` = 1) and (`danishecarter_25_march`.`cscart_product_prices`.`product_id` in (280,282,278,20,119,100,46,204,45,68,29,6,8,14,9,10,19,21,7,27,124,50,51,49,48,54,44,194,137,153,164,236,234,150,151,178,181,248,65,64,63,62,66,140,141,144,143,142,13)) and (`danishecarter_25_march`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}