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 (
    38523, 44625, 44623, 44622, 44621, 44620, 
    44619, 31996, 40662, 40658, 44618, 
    44617, 31249, 44615, 44614
  ) 
  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 0.00079

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "40.21"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "range",
        "possible_keys": [
          "membership",
          "src_k",
          "product_id",
          "lower_limit",
          "membership_id"
        ],
        "key": "product_id",
        "used_key_parts": [
          "product_id"
        ],
        "key_length": "3",
        "rows_examined_per_scan": 18,
        "rows_produced_per_join": 3,
        "filtered": "19.89",
        "index_condition": "(`ea201_diorama`.`cscart_product_prices`.`product_id` in (38523,44625,44623,44622,44621,44620,44619,31996,40662,40658,44618,44617,31249,44615,44614))",
        "cost_info": {
          "read_cost": "39.49",
          "eval_cost": "0.72",
          "prefix_cost": "40.21",
          "data_read_per_join": "85"
        },
        "used_columns": [
          "product_id",
          "price",
          "lower_limit",
          "usergroup_id",
          "percentage_discount"
        ],
        "attached_condition": "((`ea201_diorama`.`cscart_product_prices`.`lower_limit` = 1) and (`ea201_diorama`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}