What licenses for VDI do we need in our case?

We plan to implement VDI. There will be two RD virtualization hosts running Hyper-V Server 2012 R2 and two Windows Server 2012 R2 Standard hosts with Hyper-V role installed running infrastructure services (AD DS, DHCP, DNS, etc.) in virtual machines. We plan to create 120 pooled desktops running Windows 8.1. Our users use Linux based thin clients to access VDI. So what licenses do we need to purchase?

As far as I understand, we need:

• 2 x Windows Server 2012 R2 Standard licenses
• 120 VDA licenses
• 120 RDS CAL
• 120 Server CAL
• 120 Windows 8.1 licenses

Is that right? That looks way too expensive in compare with Session-based RDS (old terminal server).