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 (
    7, 11, 12, 15, 27, 28, 29, 30, 31, 32, 33, 
    34, 37, 38, 39, 40, 41, 42, 43, 47, 48, 
    49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 
    59
  ) 
  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 0.00097

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": 45.91368103,
          "index_condition": "cscart_product_prices.product_id in (7,11,12,15,27,28,29,30,31,32,33,34,37,38,39,40,41,42,43,47,48,49,50,51,52,53,54,55,56,57,58,59)",
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}