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 (
    12, 17, 148, 180, 187, 232, 230, 231, 18, 
    16, 4, 5, 23, 24, 170, 1, 22, 149, 227, 
    78, 79, 190, 189, 162, 159, 158, 245, 
    238, 239, 242, 243, 241, 240, 214, 217, 
    218, 207, 59, 58, 60, 199, 198, 94, 96, 
    201, 114, 192, 136
  ) 
  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 0.00074

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "158.57"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "96.00"
      },
      "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": "ALL",
            "possible_keys": [
              "usergroup",
              "product_id",
              "lower_limit",
              "usergroup_id"
            ],
            "rows_examined_per_scan": 296,
            "rows_produced_per_join": 95,
            "filtered": "32.43",
            "cost_info": {
              "read_cost": "43.37",
              "eval_cost": "19.20",
              "prefix_cost": "62.57",
              "data_read_per_join": "2K"
            },
            "used_columns": [
              "product_id",
              "price",
              "percentage_discount",
              "lower_limit",
              "usergroup_id"
            ],
            "attached_condition": "((`danishecarter_31jan`.`cscart_product_prices`.`lower_limit` = 1) and (`danishecarter_31jan`.`cscart_product_prices`.`product_id` in (12,17,148,180,187,232,230,231,18,16,4,5,23,24,170,1,22,149,227,78,79,190,189,162,159,158,245,238,239,242,243,241,240,214,217,218,207,59,58,60,199,198,94,96,201,114,192,136)) and (`danishecarter_31jan`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
          }
        }
      ]
    }
  }
}