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 (
    30766, 30767, 30769, 30770, 30771, 30772, 
    30773, 30774, 30775, 30776, 30777, 
    30778, 30779, 30781, 30782, 30783, 
    30784, 30785, 30786, 30787, 30788, 
    30789, 30790, 30791, 30792, 30793, 
    30794, 30795, 30796, 30797, 30798, 
    30799
  ) 
  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 0.00100

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "76.81"
    },
    "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": 32,
        "rows_produced_per_join": 6,
        "filtered": "19.99",
        "index_condition": "(`portal`.`q_product_prices`.`product_id` in (30766,30767,30769,30770,30771,30772,30773,30774,30775,30776,30777,30778,30779,30781,30782,30783,30784,30785,30786,30787,30788,30789,30790,30791,30792,30793,30794,30795,30796,30797,30798,30799))",
        "cost_info": {
          "read_cost": "75.53",
          "eval_cost": "1.28",
          "prefix_cost": "76.81",
          "data_read_per_join": "153"
        },
        "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)))"
      }
    }
  }
}