Easy, HA5RXZ and I are members of a group working on the same project and corresponding via Internet chat and email. Custom crystals are of course available but the price in small quantities is about $50 a piece.
Yeah, I know, that's why so many hams go to at least a little effort to use the $1 Microprocessor crystals :-).
Hint hint, nudge nudge.
I'm not saying there's never a need for a custom crystal, but to go and design a homebrew rig using a bunch of custom crystals, is a little like the guy who wants to build his house out of precisely machined 1.6123" x 3.9127" custom lumber instead of just using 2x4's.
Entirely possible to use all-custom frequencies, sometimes there's a good reason for the extra expense, but most of the time you just look at the funny crystal frequency you need, then look elsewhere and discover that a slight change to your original design will let you use the $1 crystals.