A:
Upgrading to 100GB Google Drive storage normally costs $5/month. It's not guaranteed that the price will remain the same after 2 years but in general, storage costs tend to go down, not up.
https://www.google.com/settings/storage/
you can upgrade to 16,000GB (16 Terabytes) of storage if you need that much (and you can afford $800/month) :-) There are numerous increments in between...
Jay