Citrix comes with 3 classes (Standard, Advanced, Enterprise)
A Citrix CAL is about $US 400 for Enterprise Edition. With 30 users, you are looking at $ 12,000 for Citrix licensing alone.
Citrix Presentation Server comes with Citrix Secure Gateway, Web Interface those components allow you to set up things in a DMZ and a web front access via port 443
I guess you already the license costs for MS Enteprise Servers, TS CALs.
It depends on what your user requirements are to deploy a solution (Citrix or non-Citrix)
Have you looked at AEP Networks and the likes?
One further question: Is it a problem to run a Citrix Presentation Server on an AD domain controller? I'm aware of the possible problems regarding GPOs, but I managed to get around them in my environment (mostly). A strict separation of Domain Controller vs. Applications Servers is way too expensive for us.