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 (
    2333, 2080, 2325, 2113, 2324, 2327, 2326, 
    2347, 2323, 2135, 2300, 2206, 2193, 
    2079, 2078, 1980, 1976, 1927, 2058, 
    1975, 1964, 2136, 2138, 2180, 2181
  ) 
  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 0.00058

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "18.86"
    },
    "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": 28,
        "rows_produced_per_join": 5,
        "filtered": "19.99",
        "index_condition": "(`cscartdevel`.`cscart_product_prices`.`product_id` in (2333,2080,2325,2113,2324,2327,2326,2347,2323,2135,2300,2206,2193,2079,2078,1980,1976,1927,2058,1975,1964,2136,2138,2180,2181))",
        "cost_info": {
          "read_cost": "18.30",
          "eval_cost": "0.56",
          "prefix_cost": "18.86",
          "data_read_per_join": "134"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`cscartdevel`.`cscart_product_prices`.`lower_limit` = 1) and (`cscartdevel`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}