SELECT 
  cscart_product_prices.product_id, 
  MIN(
    IF(
      cscart_product_prices.percentage_discount = 0, 
      cscart_product_prices.price, 
      cscart_product_prices.price - (
        cscart_product_prices.price * cscart_product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  cscart_product_prices 
WHERE 
  cscart_product_prices.product_id IN (
    2334, 2335, 2403, 2404, 2405, 2406, 2407, 
    2408, 2409, 2410, 2411, 2599, 2600, 
    2601, 2602, 5881, 5882, 5883, 5884, 
    5931, 5932, 5933, 5934, 6003, 6004, 
    6005, 6006, 6007, 6008, 6009, 6010, 
    6011, 6192, 6193, 6194, 6195, 2595, 
    2596, 2597, 2598, 6187, 6188, 6189, 
    6190, 2730, 2731, 2732, 2733
  ) 
  AND cscart_product_prices.lower_limit = 1 
  AND cscart_product_prices.usergroup_id IN (0, 1) 
GROUP BY 
  cscart_product_prices.product_id

Query time 0.00141

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "33.61"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "cscart_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": 48,
        "rows_produced_per_join": 9,
        "filtered": "20.00",
        "index_condition": "(`gaseus`.`cscart_product_prices`.`product_id` in (2334,2335,2403,2404,2405,2406,2407,2408,2409,2410,2411,2599,2600,2601,2602,5881,5882,5883,5884,5931,5932,5933,5934,6003,6004,6005,6006,6007,6008,6009,6010,6011,6192,6193,6194,6195,2595,2596,2597,2598,6187,6188,6189,6190,2730,2731,2732,2733))",
        "cost_info": {
          "read_cost": "32.65",
          "eval_cost": "0.96",
          "prefix_cost": "33.61",
          "data_read_per_join": "230"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`gaseus`.`cscart_product_prices`.`lower_limit` = 1) and (`gaseus`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}