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 (
    45360, 23044, 502, 27002, 46548, 41123, 
    23017, 26871, 1895, 47015, 1715, 26898, 
    26889, 44858, 26897, 23047, 26876, 
    47657, 40441, 5994, 47654, 4512, 26870, 
    42111, 26893, 26874, 26878, 26888, 
    26885, 6360, 26875, 37095
  ) 
  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 0.00546

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 (45360,23044,502,27002,46548,41123,23017,26871,1895,47015,1715,26898,26889,44858,26897,23047,26876,47657,40441,5994,47654,4512,26870,42111,26893,26874,26878,26888,26885,6360,26875,37095)",
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}