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 (
    822, 662, 806, 805, 804, 803, 802, 801, 
    800, 799, 796, 792, 786, 782, 744, 743, 
    742, 741, 727, 720, 718, 716, 713, 701, 
    671, 670, 664, 663, 658, 657, 656, 651, 
    377, 371, 369, 368, 362, 228, 219, 218, 
    217, 211, 207, 204, 202, 195, 192, 189, 
    71, 10, 9
  ) 
  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 0.00089

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "37.06"
    },
    "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": 54,
        "rows_produced_per_join": 10,
        "filtered": "19.93",
        "index_condition": "(`betaatif_store`.`cscart_product_prices`.`product_id` in (822,662,806,805,804,803,802,801,800,799,796,792,786,782,744,743,742,741,727,720,718,716,713,701,671,670,664,663,658,657,656,651,377,371,369,368,362,228,219,218,217,211,207,204,202,195,192,189,71,10,9))",
        "cost_info": {
          "read_cost": "35.98",
          "eval_cost": "1.08",
          "prefix_cost": "37.06",
          "data_read_per_join": "258"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`betaatif_store`.`cscart_product_prices`.`lower_limit` = 1) and (`betaatif_store`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}