1200 Vivotab RTs were sold by a single ebay seller.
Check this link which has ended currently.
Its priced at $349 for tablet with keyboard dock( extra battery). Seller has 98.9% rating.
If you see the number of units sold next to the price its 1200.
In this link all the last 100 purchases are done on 7th Feb. Most of them are 5 units (may be some of them are resellers who will sell them for a bit higher price to consumers).
Not long ago (3 months - windows 8 launch) vivotab RT was selling for $500. That price looked a bit more for RT tablet especially when you can get IPAD with more apps.
I believe over the time sales will be great as the prices of these tablets will go down.
For all of you who missed that deal can purchase the vivotab RT with keyboard dock for $398 from the below link.
This seller is top rated and has 99.6% rating.