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 (
    623, 602, 603, 683, 671, 682, 684, 685, 
    666, 664, 665, 667, 680, 604, 675, 681, 
    668, 679, 669, 670, 678, 674, 677, 676, 
    673, 672
  ) 
  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 0.00050

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "79.21"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "range",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "key": "product_id",
        "used_key_parts": [
          "product_id"
        ],
        "key_length": "3",
        "rows_examined_per_scan": 38,
        "rows_produced_per_join": 7,
        "filtered": "19.62",
        "index_condition": "(`danishecarter_latest`.`cscart_product_prices`.`product_id` in (623,602,603,683,671,682,684,685,666,664,665,667,680,604,675,681,668,679,669,670,678,674,677,676,673,672))",
        "cost_info": {
          "read_cost": "77.72",
          "eval_cost": "1.49",
          "prefix_cost": "79.21",
          "data_read_per_join": "238"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`danishecarter_latest`.`cscart_product_prices`.`lower_limit` = 1) and (`danishecarter_latest`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}