Sprint has a deal that might be attractive to some out there, but there’s a bit of math involved: customers can get access to Amazon Prime as a monthly add-on to their regular bill. Okay, cool — but then there’s the price. It’s $10.99 per month for free two-day-shipping, access to Amazon’s music and video services, and all the other stuff that comes with a Prime membership.

That monthly price adds up to $131.88 a year (h/t The Verge), which is $32.88 more than the $99 regular Prime customers pay for a year’s access.

So why would you ever want to pay more money than everyone else for something? Perhaps people may want to try Prime for more than a month but not an entire year. Because once you’ve used your Prime membership — either to buy something with two-day shipping or access Prime videos and music, etc. — you’re locked into paying that $99 for the entire year.

Or maybe you just don’t have the $99 to shell out all at one time. Both scenarios only make sense if you pay attention to how many months you’ve got under your belt with the Sprint program. Once you hit nine months, you’ll have spent only a tiny bit less than that $99 for a year, so take that into account before you end up paying too much.

The offer is available to both existing and new customers, Sprint says.

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.