SELECT 
  q_product_prices.product_id, 
  MIN(
    IF(
      q_product_prices.percentage_discount = 0, 
      q_product_prices.price, 
      q_product_prices.price - (
        q_product_prices.price * q_product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  q_product_prices 
WHERE 
  q_product_prices.product_id IN (
    30355, 30359, 30387, 30392, 30393, 30399, 
    30401, 30402, 30403, 30406, 30407, 
    30668, 30671, 30672, 30675, 30676, 
    30682, 30686, 30694, 30695, 30699, 
    30701, 30702, 30704, 30705, 30707, 
    30708, 30711, 30712, 30713
  ) 
  AND q_product_prices.lower_limit = 1 
  AND q_product_prices.usergroup_id IN (0, 1) 
GROUP BY 
  q_product_prices.product_id

Query time 0.00091

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "102.81"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "q_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": 52,
        "rows_produced_per_join": 10,
        "filtered": "19.99",
        "index_condition": "(`portal`.`q_product_prices`.`product_id` in (30355,30359,30387,30392,30393,30399,30401,30402,30403,30406,30407,30668,30671,30672,30675,30676,30682,30686,30694,30695,30699,30701,30702,30704,30705,30707,30708,30711,30712,30713))",
        "cost_info": {
          "read_cost": "100.73",
          "eval_cost": "2.08",
          "prefix_cost": "102.81",
          "data_read_per_join": "249"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`portal`.`q_product_prices`.`lower_limit` = 1) and (`portal`.`q_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}