It's an impressive feat for Tex to not only bring in the original asking figure of $450,000, but to surpass it by over $200,000. A congratulations to Big Finish for managing to brining in so much, and certainly a thanks to everyone who backed this project is called for, so: Thanks!
No specific reason has been given for closing off contributions, but with a publisher becoming involved, it's probable that at some point they would rather sell pre-order copies at more than $15 a piece. I'm sure once all the distribution issues are settled, pre-order will become available.
Based on what has been flying around the forums and from Chris Jones's interview on Wednesday, Steam seems to be the main target for distribution, which is great. Steam has a huge user base to expose Tex to. As I write this, there are currently 4.8 million people logged on to Steam. I wouldn't be surprised if we see Tesla Effect show up on GOG as well.
Here's hoping Tesla Effect is a huge success!