XE.com rates are "mid-market rates" - i.e. they are not rates you can transact at. So it's really not fair to compare XE.com rates to any retail buy/sell rate.
From the XE.com site:
The rates in our free information services are neither "buy" nor "sell" rates. Instead, they are mid-market rates derived from the mid-point between the "buy" and "sell" rates from global currency markets. Our free information services always list the mid-market rate because it indicates the value of a currency that is not weighted towards buying or selling. "Buy" and "sell" rates include overheads and profit margins that are independently set by foreign exchange providers; their rates can vary a lot and will differ from the mid-market rate, so we recommend you shop around.