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 (
    8195, 3781, 3782, 3783, 3784, 3773, 3774, 
    3775, 3776, 3777, 3778
  ) 
  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 0.00058

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "26.41"
    },
    "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": 11,
        "rows_produced_per_join": 2,
        "filtered": "19.99",
        "index_condition": "(`portal`.`q_product_prices`.`product_id` in (8195,3781,3782,3783,3784,3773,3774,3775,3776,3777,3778))",
        "cost_info": {
          "read_cost": "25.97",
          "eval_cost": "0.44",
          "prefix_cost": "26.41",
          "data_read_per_join": "52"
        },
        "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)))"
      }
    }
  }
}