I did hear of a university where, due to the number of macs they purchased, they wrangled free3-year APP on all of their purchase.

Maybe it's worth reaching out to your Apple Rep and playing friendly with them?

That would be cool but I highly doubt it. You would need to be purchasing thousands of Macs and paying for some pretty high level support before that kind of deal broke out. I couldn't see that happening on 500 macs though you would get yourself a good 13-15% off I would imagine (ON top of the edu pricing). So, 3 year AC on something like $150-ish on a 13" MacBook Air when all is said and done.

what about deployment? what is your workflow from "new-in-a-box" to in a user's hands?

Figure out exactly what software you want to install/need. Figure out any restrictions you want to apply, and how (Config Profile, script, Restricted Software, MCX). Both of these may be applicable to specific groups of users (i.e. teachers vs students vs office/admin people). Actually testing these beforehand (especially from a security perspective, also setting Firmware passwords), so that your image is fairly done/secure/polished before you deploy it widely (rather than having to apply fixes to machines already imaged out into the field.

Thin image (i.e. don't replace the OS, just update it) vs Thick (wipe machine and replace it).

Think about how you'll handle machine repair or replacement, and also reimaging to address issues.

If the Macs will be running testing apps, you will have even more considerations relating to Java, user account, Dock, etc.