SELECT 
  cscart_multi_decproduct_prices.product_id, 
  MIN(
    IF(
      cscart_multi_decproduct_prices.percentage_discount = 0, 
      cscart_multi_decproduct_prices.price, 
      cscart_multi_decproduct_prices.price - (
        cscart_multi_decproduct_prices.price * cscart_multi_decproduct_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  cscart_multi_decproduct_prices 
WHERE 
  cscart_multi_decproduct_prices.product_id IN (
    53, 52, 111, 82, 84, 228, 85, 88, 26, 35, 
    47, 81, 107, 109, 91, 92, 161, 188, 202, 
    203, 34, 31, 38, 80
  ) 
  AND cscart_multi_decproduct_prices.lower_limit = 1 
  AND cscart_multi_decproduct_prices.usergroup_id IN (0, 1) 
GROUP BY 
  cscart_multi_decproduct_prices.product_id

Query time 0.00066

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "56.00"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "table": {
        "table_name": "cscart_multi_decproduct_prices",
        "access_type": "ref",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "key": "lower_limit",
        "used_key_parts": [
          "lower_limit"
        ],
        "key_length": "3",
        "ref": [
          "const"
        ],
        "rows_examined_per_scan": 235,
        "rows_produced_per_join": 4,
        "filtered": "1.89",
        "index_condition": "(`vishalecarter_multi_dec`.`cscart_multi_decproduct_prices`.`lower_limit` <=> 1)",
        "cost_info": {
          "read_cost": "9.00",
          "eval_cost": "0.89",
          "prefix_cost": "56.00",
          "data_read_per_join": "106"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`vishalecarter_multi_dec`.`cscart_multi_decproduct_prices`.`product_id` in (53,52,111,82,84,228,85,88,26,35,47,81,107,109,91,92,161,188,202,203,34,31,38,80)) and (`vishalecarter_multi_dec`.`cscart_multi_decproduct_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}