What is an upgrade to ViewPoint

I am currently running the free trial of ViewPoint, and was planning to buy it today. The email I just got about the Black Friday price reduction is therefore good news, but I’m a bit confused by the fact that there seems to be a new price (£34.99) and an upgrade price (£19.99) quoted. I thought upgrade prices were for existing customers who were users of a previous version of a new release. But since VP has not been updated for a while, why would an existing user want to “upgrade”?

Current VP version is 3.
You can have VP1 or VP2 and pay only a upgrade.
You’re right, no many users must have a old realease.

Thanks, that makes sense.