The chamfer cutter you referenced is for chamfering the forcing cone on a revolver, not repairing a damaged crown.

If you've got access to a lathe and are comfortable performing the work (and don't need to remove the barrel to get it chucked and concentric), then recutting the crown yourself is the quickest and surest way to get it fixed.

The reason you're getting high estimates is that most gunsmiths would insist on removing the barrel to do the job properly, and that (and reinstalling it after) is rather a big job in itself.

Brownells does have crown cutters for sale that will chuck into an electric drill, and you could use those without removing the barrel - but since that's a hand-steadied cutting job, it won't be as precise as a lathe job.

I've also heard of people recrowning with a marble and valve grinding compound - slather some grit onto a marble and work it for a few hours by hand while watching TV or something. It also won't be as precise as a lathe job, but is easier to center, and the resulting, curved crown would at least be better than the damaged crown you have now.