US Airways is bringing back the 100% bonus on gifting and buying miles. It's good for up to 50,000 miles.
Given the bonus buying 50,000 miles will result in a net addition of 100,000 miles to your Dividend Miles account. That's enough for a round-trip in Business Class to Europe.
The price comes to $1,750 + 7.5% in taxes.
It's a good price if you need a chunk of miles for an upcoming redemption. Otherwise Avianca's deal is better IF you can make the routing restriction work for you (i.e. same class of service must be available for all segments).