Compare internet value in cost per GB.
There are two honest cost-per-gigabyte figures and providers quote the flattering one. Dividing the bill by the included allowance gives the advertising number, which falls the moment a plan bundles more data whether or not anyone uses it. Dividing by the data you actually consume gives the figure you really pay, and it is always the higher of the two whenever the allowance goes unused. The gap between them, multiplied by the unused gigabytes, is money spent on headroom. Comparing plans on cost per used gigabyte — with router rental, line fees and taxes folded into the total, since those are unavoidable — is the only comparison that survives a change of provider.
True and advertised cost per gigabyte
Total monthly = plan fee + extra fees; cost per used GB = total monthly / min(usage, allowance); cost per included GB = total monthly / allowance; wasted spend = cost per included GB x (allowance - usage)
Cost per gigabyte you actually use. Advertised cost per included gigabyte rewards plans for bundling allowance you will never consume, which is why unlimited plans always look cheapest on that basis.
Only if your usage is stable and the smaller plan is meaningfully cheaper. Check the overage rate first — one heavy month can cost more than a year of the headroom you gave up.
Because you cannot avoid them and they differ sharply between providers. A cheaper headline fee with mandatory equipment rental frequently loses to a dearer all-inclusive plan.