Well take a look at what you're getting...
As far as the board goes, it's on par with the offerings from Asus, A-Bit, Epox, etc, and in some cases better!
99 IMO is a steal for this board. With the options it has (Nforce Ultra 400, RAID, 6chan sound, etc), and the performance in general, it is a much, much better deal than an equivelant board from another manufacturer.
I just ordered one of Newegg, and I've used the first revision of this board (w/out the RAID), and 99$ for this one is a steal.
So why the price going up? Soltek is not a big name when it comes to motherboards. I don't know many people that have heard of them. They initially sold the boards dirt cheap to build up a reputation. As that reputation and customer-base grows, the board's price goes up.
I wouldn't be suprised to see the board at 110$ or more before long. If what other people are saying is correct, Soltek is no longer selling boards to the US, which may also justify the recent price increase.