You purchased an app and that app will run for years, possibly for decades, until your operating system stops supporting it. It won't cost you a penny more than you already paid. But why, (and I don't mean this to sound nasty), would you feel entitled to the newer version of the app for free too?
To use a car buying analogy (since you mentioned cars)... you paid for Version 1. To expect Version 2 for nothing is the equivalent of taking your car back to the garage after a couple of years and expecting them to upgrade your CD player and fit new alloys for nothing. Not likely, is it? :) You paid for version 1, and that's what you got. Version 2 will have new and enhanced features. If you want those features, you're going to have to pay for the upgrade (though I would bet Affinity will offer a decent discount to existing licence holders).
Not trying to give you a hard time, but I don't think it's realistic to expect unlimited upgrades for the amount you paid.