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 (
    296884, 296840, 296925, 296885, 296815, 
    296844, 296874, 296922, 296903, 296924, 
    296930, 296843, 296902, 296910, 296891, 
    296863, 296923, 296850, 296887, 296816, 
    296916, 296813, 296856, 296854
  ) 
  AND product_prices.lower_limit = 1 
  AND product_prices.usergroup_id IN (0, 1) 
GROUP BY 
  product_prices.product_id

Query time 0.00550

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "21.22"
    },
    "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 (296884,296840,296925,296885,296815,296844,296874,296922,296903,296924,296930,296843,296902,296910,296891,296863,296923,296850,296887,296816,296916,296813,296856,296854))",
        "cost_info": {
          "read_cost": "20.98",
          "eval_cost": "0.24",
          "prefix_cost": "21.22",
          "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)))"
      }
    }
  }
}