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 (
    9544, 9592, 9593, 9594, 9595, 9596, 9597, 
    9598, 9599, 9600, 9601, 9602, 9603, 
    9604, 9605, 9606, 9607, 9608, 9609, 
    9610, 9611, 9612, 9613, 9614, 9615, 
    9616, 9617, 9618, 9619, 9620, 9621, 
    9622
  ) 
  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 0.00074

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "90.81"
    },
    "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": 42,
        "rows_produced_per_join": 8,
        "filtered": "19.99",
        "index_condition": "(`portal`.`q_product_prices`.`product_id` in (9544,9592,9593,9594,9595,9596,9597,9598,9599,9600,9601,9602,9603,9604,9605,9606,9607,9608,9609,9610,9611,9612,9613,9614,9615,9616,9617,9618,9619,9620,9621,9622))",
        "cost_info": {
          "read_cost": "89.13",
          "eval_cost": "1.68",
          "prefix_cost": "90.81",
          "data_read_per_join": "201"
        },
        "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)))"
      }
    }
  }
}