Try to pin down a price for VSTS from a Microsoft employee is impossible. The latest news is that a firm price will be announced in March 2005.
The bad news is that MSDN subscriptions are going to change and if you want VSTS it is going to cost you more $$$. How much more? See the first paragraph, Microsoft won't say. If strongly pressed I have heard this from MS employees. The VSTS MSDN subscription will be somewhere between 1.25 and 2.0 times the cost of a current universal MSDN subscription.