I downloaded/installed 5, uninstalled 4.

But I am unable to find a web page for paying for the 4=>5 upgrade.

No such thing?

Am I going to save a buck or just pay the seventy bucks for v5?

Yes there is. Go to https://blueirissoftware.com/#purchase

Select any of the three

• Extend support & maintenance ($29.95 /yr)

• Priority & maintenance ($59.95 /yr)

• 1 yr. extension of support & maintenance ($34.95 one time)

*Any of these will upgrade a version 4 key to version 5 (indefinitely)