It's nothing to do with money per se, but more to do with bloody legal. Epic's legal department just flat-out won't comply. I think someone said it was becuase some old code could be copied by licensees of the Unreal Engine, as well as other developers. I think that it was said that some of the code in the betas is super-special for some reason.
Looking at code from a beta of a game from 1996 would not help anyone in their project. It's UScript, so It's only useful in games that utilise the Unreal Engine. Not only that, but since the game is unfinished the code would be too. Nobody would want to try and fix all the errors to make it totally playable. That's why the full game was released! A remake in UDK would be illegal, just like a UT remake (But who would want to remake a beta of a game?) The code is seriously, SERIOUSLY deprecated and anyone trying to use it in, let's say, a UDK project for example, would not be able to due to the age gap. 15 year old game code from an unfinished game engine over 10 years old would be of no use to anyone. Why would someone set out to translate the beta code to UnrealEngine 3 standards, actually manage to compile it AND sell their project they created while giving NO credit to Epic, where it would have been so much quicker to write the needed function themselves?
Take the already-leaked '95 Tech Demo and 97/98 beta. The tech demo has snazzy music and shows off the potential of the Unreal Engine and the 97/98 beta has a few different levels, sounds, music and textures but seriously, who thinks Epic would have lost any money becuase of these leaks? The beta has netplay disabled and the tech demo doesn't even have netplay! The tech demo has 0 Single Player experience and the Beta crashes, has horrible controls and is glitchy. If anything, seeing these betas would encourage people to buy the full thing.
I understand where their Legal department is coming from. It's not as easy as "Ok, heres the betas. *Hands over link to FTP*". LOTS of contracts would have to be signed. I personally think that the release of the source code (The code that CREATED Unreal) is more risky than allowing public access of the Alphas and Betas. They don't even need to release them entirely. Like Leo said, they could release specific files and the content could be ported over as a mod (Completely seperate from 227 of course.)
A "All guns blazing" bethod to obtain these in my opinion, would be for as many people as possible to write a small part about why they would like the Betas, (Pros, Cons etc...) or for everyone to sign a petition. If Smirf (Or someone who would likely get a reply from Epic) could E-Mail this to Epic, then maybe they might see reason and an agreement could be made.
tl;dr
Legal department won't allow it becuase they don't want to risk losing a few pounds (Dollars...w/e)