I too micromanage my data and pay for overages. Firefox updates, assuming you don't skip them, are actually quite reasonably sized, averaging about 10MB a month

I too micromanage my data and pay for overages. Firefox updates, assuming you don't skip them, are actually quite reasonably sized, averaging about 10MB a month for me over the last few of years, both major version revs and minor security updates combined. I consider my online security worth those 10MB because I've never been able to manage my bandwidth to the kind of precision where 10MB one way or the other would have made a meaningful distance in my bill.