SELECT 
  cscart_product_prices.product_id, 
  COALESCE(
    cscart_master_products_storefront_min_price.price, 
    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 
  LEFT JOIN cscart_master_products_storefront_min_price ON cscart_master_products_storefront_min_price.product_id = cscart_product_prices.product_id 
  AND cscart_master_products_storefront_min_price.storefront_id = 1 
WHERE 
  cscart_product_prices.product_id IN (
    227, 241, 240, 214, 217, 218, 207, 205, 
    208, 229, 211, 210, 209, 213, 215, 226, 
    228, 247, 244, 212, 206, 223, 225, 224, 
    219, 222, 220, 221
  ) 
  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 0.00090

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "67.00"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_master_products_storefront_min_price",
            "access_type": "system",
            "possible_keys": [
              "PRIMARY"
            ],
            "rows_examined_per_scan": 0,
            "rows_produced_per_join": 1,
            "filtered": "0.00",
            "const_row_not_found": true,
            "cost_info": {
              "read_cost": "0.00",
              "eval_cost": "0.20",
              "prefix_cost": "0.00",
              "data_read_per_join": "16"
            },
            "used_columns": [
              "storefront_id",
              "product_id",
              "price"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_product_prices",
            "access_type": "ref",
            "possible_keys": [
              "usergroup",
              "product_id",
              "lower_limit",
              "usergroup_id"
            ],
            "key": "lower_limit",
            "used_key_parts": [
              "lower_limit"
            ],
            "key_length": "3",
            "ref": [
              "const"
            ],
            "rows_examined_per_scan": 290,
            "rows_produced_per_join": 5,
            "filtered": "1.89",
            "index_condition": "(`danishecarter_31jan`.`cscart_product_prices`.`lower_limit` <=> 1)",
            "cost_info": {
              "read_cost": "9.00",
              "eval_cost": "1.10",
              "prefix_cost": "67.00",
              "data_read_per_join": "131"
            },
            "used_columns": [
              "product_id",
              "price",
              "percentage_discount",
              "lower_limit",
              "usergroup_id"
            ],
            "attached_condition": "((`danishecarter_31jan`.`cscart_product_prices`.`product_id` in (227,241,240,214,217,218,207,205,208,229,211,210,209,213,215,226,228,247,244,212,206,223,225,224,219,222,220,221)) and (`danishecarter_31jan`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
          }
        }
      ]
    }
  }
}