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 (
    33702, 2157, 1519, 45357, 1895, 47654, 
    5832, 47601, 1586, 47658, 3388, 37304, 
    38143, 5837, 27357, 38152, 27358, 40824, 
    49306, 27360, 2471, 41170, 1429, 5834, 
    27362, 6560, 36399, 6561, 4894, 1042, 
    1534, 41231
  ) 
  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 0.00565

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 (33702,2157,1519,45357,1895,47654,5832,47601,1586,47658,3388,37304,38143,5837,27357,38152,27358,40824,49306,27360,2471,41170,1429,5834,27362,6560,36399,6561,4894,1042,1534,41231)",
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}