Rail Simulator and RailWorks are owned by different Owners / Companies now and considered as different programs.
Rail Simulator is no longer officially updated or Developed. Rail Simulator is not able to upgrade to RailWorks.
If you want RailWorks (or as they call it now, RailWorks3 / Train-Simulator2012), you'll need to buy it separately and at whatever price it is.
Oft times Steam has Christmas sales. Though I can't say for sure, but if you check Steam during the Christmas sales, you might be able to get the current RailWorks3/Train-Sim2012 for a discounted price.
http://store.steampowered.com/app/24010/Read the details on that page for what's included with it.