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, 60, 62, 63, 64, 65, 67, 68, 69, 70, 
    71, 72, 73, 74, 75, 76, 78, 79, 80, 81, 
    82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 
    92, 93, 94
  ) 
  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 0.00530

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "cscart_product_prices.product_id",
      "temporary_table": {
        "nested_loop": [
          {
            "table": {
              "table_name": "cscart_product_prices",
              "access_type": "ALL",
              "possible_keys": [
                "usergroup",
                "product_id",
                "lower_limit",
                "usergroup_id"
              ],
              "rows": 264,
              "filtered": 22.26117897,
              "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.product_id in (7,11,12,15,27,28,29,30,31,32,33,34,37,38,39,40,41,42,43,47,48,49,50,51,52,53,54,55,56,57,58,59,60,62,63,64,65,67,68,69,70,71,72,73,74,75,76,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94) and cscart_product_prices.usergroup_id in (0,1)"
            }
          }
        ]
      }
    }
  }
}