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 (
    27361, 1893, 47593, 49169, 38074, 6091, 
    6370, 49164, 49230, 48846, 47631, 42255, 
    40350, 2803, 47655, 5789, 33312, 5300, 
    5297, 1103, 65, 47024, 1102, 1104, 47020, 
    47023, 47022, 27353, 6369, 48558, 3862, 
    6368
  ) 
  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 0.00355

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_prices",
          "access_type": "range",
          "possible_keys": [
            "usergroup",
            "product_id",
            "lower_limit",
            "usergroup_id"
          ],
          "key": "product_id",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "rows": 32,
          "filtered": 99.9960556,
          "index_condition": "cscart_product_prices.product_id in (27361,1893,47593,49169,38074,6091,6370,49164,49230,48846,47631,42255,40350,2803,47655,5789,33312,5300,5297,1103,65,47024,1102,1104,47020,47023,47022,27353,6369,48558,3862,6368)",
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}