^I wish I could afford Mayer's signature Martin..
But yeah I agree with what you're saying about how Martin is all about the brand name. The quality of woods used can only get so high before the breaking point of just paying for the name/signature.
Honestly the only acoustic guitars I think that are actually worth it in terms of quality and bang for your buck, are Morgan and Larivee. Seagull and Art&Lutherie aren't bad either. Don't even bother with acoustic Gibsons and Fenders.
Don't even get me started on electrics.