My startup uses .Net which I chose for the basic reason that I know it very well and I didn't have time to go learn something else while I was trying to get work done. Any server I add is in response to more paying customers so the cost doesn't matter at all. It cuts into the margin a little but I only add new servers when we add a lot of new business. The initial cost of VS.Net was annoying but it wasn't bad and I was able to run off of SQL Server 2008 Express for a very long time.