Hi Jay!
My situation is different versus others. I still have my original (grandfathered) unlimited 4G LTE data plan by Verizon before they cancelled their unlimited data in the same way AT&T did.
That means I don't have to worry about overage charges if going past say a 2, 4, 6+ GB tiered plan. Therefore I don't worry about how much data I use.
If I didn't have unlimited data and only have a small data plan, then I'd have to worry about paying something like $10 for each 1GB over my monthly allotment.
As for Foxfi, this Android app allows me to use the mobile wifi hotspot feature on my Verizon Android smartphone with-OUT having to pay Verizon the normal $30 monthly fee for the service.
Actually, anyone can elect to pay Verizon the optional $30 fee for activating a smartphone's mobile wifi hotspot feature (assuming if the phone is capable of this). But as soon as a user goes over a certain data plan limit, there will be an overage fee per each gigabyte over the limit.
For a Verizon customer with an Android smartphone, a user can pay the flat $8 fee for the Foxfi app (through the phone's Google Playstore app), and use the "un-authorized" wifi tethering service. This would effectively bypass paying Verizon the normal $30 monthly fee for the hotspot feature. But again, keep in mind that if a user doesn't have unlimited data (which most people don't unless grandfathered), there will be an overage fee for going over whatever monthly GB plan limit.
I realize there are multiple variables involved with the above scenario, but hopefully all that made sense.