Originally Posted by
CocoPops
are 50k miles worth £400?
Yes, definitely worth more than that, especially when you don't have that many of them.
If you really want to go to New York then unless you're in a tearing hurry I really think you are better off waiting for the next CW sale and saving the miles (and banking, of course, a whole bunch more from the NY trip). There are worse uses of miles than you're suggesting, but there are also much better ones right now. A couple of years ago, when CW sales were rarer, less generous, and only (between them) covered travel on a limited range of dates, I would not have said this so readily.
A reasonable alternative would be to wait for a WTP sale and see if you can get MFUs then.