1. When you say case costs are you including the various finishing bits and pieces or do you just mean raw chassis including panel fab? If it's the latter and you go single chassis figure $200 for just the bones. The chassis once it gets shipped will probably run ~$100 and having both panels done will probably run another $100 (maybe less, maybe more). Of course that leaves you a long way from a finished case but you know that. I'd bet I spent ~$300 on Mike's beta22 including the knobs, switches, RCA's, IEC, etc.
2. You do not want to be mounting the trafo to a PCB, or at least I wouldn't. For me and my money and with the size of the sucker you're talking here I'd want that beast bolted to metal and no chance of shock loading a solder joint or pcb with anything else attached to it.