Just curious because our budget is really small, would Unity ever drop the price of pro for Unity 3 since it would be an older technology or would they just discontinue it?
You buy a license to use rather than an owned version with most software, I’d assume that Unity is the same. In which case I think it’s highly unlikely you’ll see UT selling Unity3 licenses from this point forwards, however I’ve no idea what their rules are regards resale, so it’s possible that someone else may sell you their “second hand” license for a Pro version of 3.
Reselling licenses is against the EULA.
I don’t think I know of any company that sells older versions of their software at discounted prices. It’s an interesting concept… we could still be selling Unity 1.0 for $15 or something 
I don’t see us doing this anytime soon though.
It’s probably better to shift support over to newer versions than sell older versions and spread support thin over all of them, anyway.