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 (
    10965, 10985, 11005, 11027, 11047, 11067, 
    11089, 11111, 11133, 11153, 11173, 
    11195, 11215, 11237, 11259, 11279, 
    11299, 11320, 11813, 11819, 11825, 
    11831, 11838, 11844, 11851, 11869, 
    11887, 11909, 11929, 11936, 11940, 
    11944, 11951, 11958, 11959, 11960, 
    11961, 11962, 11963, 11964, 11965, 
    12030, 12031, 12032, 12033, 12034, 
    12035, 12036
  ) 
  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 0.00163

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "37.66"
    },
    "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": 57,
        "rows_produced_per_join": 11,
        "filtered": "20.00",
        "index_condition": "(`gaseus`.`cscart_product_prices`.`product_id` in (10965,10985,11005,11027,11047,11067,11089,11111,11133,11153,11173,11195,11215,11237,11259,11279,11299,11320,11813,11819,11825,11831,11838,11844,11851,11869,11887,11909,11929,11936,11940,11944,11951,11958,11959,11960,11961,11962,11963,11964,11965,12030,12031,12032,12033,12034,12035,12036))",
        "cost_info": {
          "read_cost": "36.52",
          "eval_cost": "1.14",
          "prefix_cost": "37.66",
          "data_read_per_join": "273"
        },
        "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)))"
      }
    }
  }
}