jbard: I think their is another point here as well as the extra costs. The people who are in range of VDSL2 are already close to a cabinet so excluding house wiring will be getting very good ADSL2+ speeds, so the only real world benefit is the faster upload. Really I imagine most people would not be keen to pay $500+ for the extra upload when fibre could be at their door in a few years time.
If you're getting good ADSL2+ download speeds though, you will get even better VDSL2 download speeds. At the end of the day there is still a big difference between 17Mbps and 40Mbps if you're a big household with multiple devices and are heavy consumer of content.