I shot my very first F-Class match yesterday, and it is definitely not condusive to barrel life!! 20 rounds in 30 minutes had the 30-338 Lapua's 1.35" dia. barrel practically smokin!
Life would be better with the others, as they use less powder, performance is the trade off though. Keeping your barrel COOL as practical is the ultimate answer though.
Rechambering will generally run $150-250 depending on who does it. Muzzle brake
will vary depending on whether it is a threaded or integral type, and the smith's rate. Threaded on brakes vary in price, so this is a good part of the total you'll shell out.
Another option -
If you don't feel the 7 Ultra is really needed, but you'd still like to hang onto the barrel for some real long range use at times, find a take off barrel in the fat cased 7 WSM or 7 SAUM (they will feed fine as is) and have the barrels set up for a pinned aftermarket recoil lug and both headspaced to your action. Chris could probably hook you up for a better price than you might think just setting the barrels back for a shorter throat/re-shouldering for the new lug and fitting to your action giving you exactly what you need to change barrels when you want to. I may have a CM 7 mag take off barrel, but I'd use the 7 WSM chamber to insure it feeds without modification, as you'll still want the Ultra to feed... assuming you go this route and is something you're even interested in.
If you can find a 7 WSM barrel locally that will actually headspace correctly, or wind up a little on the loose/exessive side with your existing recoil lug, you can accomplish this with even less $$.