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 (
    1893, 47593, 47631, 33312, 65, 43825, 
    47656, 48998, 2292, 47654, 47984, 40761, 
    3471, 47660, 1781, 1755, 3620, 35254, 
    47598, 47599, 6367, 35188, 35859, 1784, 
    40760, 5998, 2233, 4465, 4362, 1756, 
    28157, 6543
  ) 
  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 0.00212

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 (1893,47593,47631,33312,65,43825,47656,48998,2292,47654,47984,40761,3471,47660,1781,1755,3620,35254,47598,47599,6367,35188,35859,1784,40760,5998,2233,4465,4362,1756,28157,6543)",
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}