Forgot to mention is another advantage of the breechlock is you can test the iris stopping down which you can't do easily with the FDN.....probably why in a pawn shop (many years ago) saw in the window a FDN 50mm f1.8 for £1.80(
why not round it up to £2
), with everything locked on the lens it would appear it wasn't working.
Primes too expensive? There are always zooms going cheaper and I have quite a few and favourites I use....but as mentioned before there is the problem of copy variation and I've been caught out in the past when e.g. everyone was raving about the Vivitar series 1 zooms, so bought one (Tokina) and my copy was crap and gave it to a charity shop.