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 (
    1896, 50216, 40451, 49588, 2320, 2319, 
    35256, 47632, 45283, 46822, 6659, 50182, 
    48823, 46585, 15457, 40927, 49012, 
    47903, 43817, 1894, 49873, 6358, 6357, 
    41341, 35279, 47597, 1767, 18608, 1057, 
    5790, 17265, 41340
  ) 
  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 0.00967

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 (1896,50216,40451,49588,2320,2319,35256,47632,45283,46822,6659,50182,48823,46585,15457,40927,49012,47903,43817,1894,49873,6358,6357,41341,35279,47597,1767,18608,1057,5790,17265,41340)",
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}