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 (
    10065, 10066, 10067, 10068, 10069, 10070, 
    10071, 10072, 10073, 10074, 10075, 
    10076, 10077, 10078, 10079, 10080, 
    10081, 10082, 10083, 10084, 10085, 
    10086, 10087, 10088, 10089, 10090, 
    10091, 10092, 10093, 10094, 10095, 
    10096, 10097, 10098, 10099, 10100, 
    10101, 10102, 10103, 10104, 10105, 
    10106, 10107, 10108, 10109, 10110, 
    10111, 10420
  ) 
  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 0.00130

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "33.61"
    },
    "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": 48,
        "rows_produced_per_join": 9,
        "filtered": "20.00",
        "index_condition": "(`gaseus`.`cscart_product_prices`.`product_id` in (10065,10066,10067,10068,10069,10070,10071,10072,10073,10074,10075,10076,10077,10078,10079,10080,10081,10082,10083,10084,10085,10086,10087,10088,10089,10090,10091,10092,10093,10094,10095,10096,10097,10098,10099,10100,10101,10102,10103,10104,10105,10106,10107,10108,10109,10110,10111,10420))",
        "cost_info": {
          "read_cost": "32.65",
          "eval_cost": "0.96",
          "prefix_cost": "33.61",
          "data_read_per_join": "230"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`gaseus`.`cscart_product_prices`.`lower_limit` = 1) and (`gaseus`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}