SELECT 
  product_prices.product_id, 
  MIN(
    IF(
      product_prices.percentage_discount = 0, 
      product_prices.price, 
      product_prices.price - (
        product_prices.price * product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  product_prices 
WHERE 
  product_prices.product_id IN (
    241402, 242084, 238468, 238494, 238463, 
    238437, 238479, 238471, 238457, 238445, 
    238472, 238453, 238444, 238475, 238446, 
    238461, 238465, 238470, 238487, 238492, 
    238440, 238481, 238486, 238467
  ) 
  AND product_prices.lower_limit = 1 
  AND product_prices.usergroup_id IN (0, 1) 
GROUP BY 
  product_prices.product_id

Query time 0.00116

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "19.50"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "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": 24,
        "rows_produced_per_join": 2,
        "filtered": "10.00",
        "index_condition": "(`goimagine`.`product_prices`.`product_id` in (241402,242084,238468,238494,238463,238437,238479,238471,238457,238445,238472,238453,238444,238475,238446,238461,238465,238470,238487,238492,238440,238481,238486,238467))",
        "cost_info": {
          "read_cost": "19.26",
          "eval_cost": "0.24",
          "prefix_cost": "19.50",
          "data_read_per_join": "57"
        },
        "used_columns": [
          "id",
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`goimagine`.`product_prices`.`lower_limit` = 1) and (`goimagine`.`product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}