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 (
    20221, 20222, 20223, 21286, 21287, 21288, 
    21289, 21290, 21291, 22177, 21514, 
    22151, 21292, 21293, 21342, 21294, 
    21295, 21343, 21296, 21297, 21344, 
    22152, 22153, 21345, 21346, 21347, 
    21348, 22154, 22155, 22156, 22159, 
    21349, 21350, 22157, 22158, 21552, 
    21553, 21351, 21488, 21352, 21353, 
    21354, 21298, 21355, 21299, 21300, 
    21301, 21302, 22160, 21303, 22175, 
    21356, 21357, 22161, 21304, 21305, 
    21306, 21307
  ) 
  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 0.01217

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "cscart_product_prices.product_id",
      "temporary_table": {
        "nested_loop": [
          {
            "table": {
              "table_name": "cscart_product_prices",
              "access_type": "ref",
              "possible_keys": [
                "usergroup",
                "product_id",
                "lower_limit",
                "usergroup_id"
              ],
              "key": "lower_limit",
              "key_length": "3",
              "used_key_parts": ["lower_limit"],
              "ref": ["const"],
              "rows": 11706,
              "filtered": 58.46075058,
              "attached_condition": "cscart_product_prices.lower_limit <=> 1 and cscart_product_prices.product_id in (20221,20222,20223,21286,21287,21288,21289,21290,21291,22177,21514,22151,21292,21293,21342,21294,21295,21343,21296,21297,21344,22152,22153,21345,21346,21347,21348,22154,22155,22156,22159,21349,21350,22157,22158,21552,21553,21351,21488,21352,21353,21354,21298,21355,21299,21300,21301,21302,22160,21303,22175,21356,21357,22161,21304,21305,21306,21307) and cscart_product_prices.usergroup_id in (0,1)"
            }
          }
        ]
      }
    }
  }
}