Its $50 one time purchase for new purchase. The upgrade from Arq 4 is $25. During store checkout, you can also choose to add a "Lifetime Upgrades" at $30 which will give you free upgrades for Arq 6, 7, 8, 9, 10, 11, 12 etc.
I purchased the Lifetime Upgrades in September 2015. Now it tells me there is a $25 upgrade fee to go to version 5. I emailed support a few hours ago to confirm. If this is true, I am extremely disappointed and feel cheated. Notice on the form to buy a new license it doesn't say anything about "Lifetime Upgrades for this major version _only_ which will be obsolete in a few months". I sure hope this is just a bug that they will fix.
