Short answer: the software and the storage are two separate purchases, and most services sell them as one so the bill grows with your data.
Purchase the software once, and use disks you already own. The arithmetic below is the whole argument.
Every backup arrangement has a piece of software that decides what to copy and when, and a place the copy goes. They are separable, and whether a company separates them tells you most of what you need to know about the price.
Do it over five years, because that is roughly how long a backup arrangement lasts before you change machines, and because a monthly figure is designed not to be multiplied.
A storage subscription at around $9 a month is $540 over five years, and that is the flat-rate case. Anything priced per terabyte grows as your photo library does, which is the direction photo libraries go.
Against that: a 4 TB external drive is roughly $90 to $110 once, and a second one for the off-site copy takes it to about $200. Software purchased outright is typically $40 to $80. Call the whole thing $250 to $300 over the same five years, and you own the disks at the end.
Two honest adjustments. Drives fail, so budget on replacing one in that window. And if you already pay for iCloud, Google One, Dropbox, OneDrive or Proton for other reasons, the off-site half may already be paid for, in which case the comparison gets more lopsided still.
It buys real things, and pretending otherwise is how you end up with worse advice than you started with.
If you will not maintain a second drive, a subscription is genuinely the better answer for you, and the honest recommendation is to purchase one.
The version we would argue for, and it is not complicated:
That satisfies the 3-2-1 rule with no new recurring cost, which is the whole point.
Free for one backup location, with no trial to run out. Free includes the whole backup, the whole restore and the verification pass, which is to say the parts you would be upset to lose.
Pro is $4.99 a month, $39.99 a year or $79.99 once, and adds more than one location, browsing older versions, recovering deleted files and scheduled deep checks. We sell the monthly option because some people prefer it, and the lifetime price is there because a backup tool you pay for forever is the thing this page is arguing against.
There is no storage bill from us at any tier, because we have no storage to sell. The amount you back up changes nothing about what you pay. And the format is documented with a free tool that reads a backup without us, so the software being a one-off purchase is the same idea applied twice.
No. At a flat rate for one machine it is one of the better-priced services there is, and the off-site copy is handled for you. The question this page asks is different: whether you want a bill that never ends for something you could own, and whether you will actually keep a drive if you go the other way.
Carbon Copy Cloner, SuperDuper, ChronoSync and Arq all sell outright, and so does Copy Shelter at $79.99. Check current pricing on each vendor's own site. We are a competitor.
For one local copy, on a drive at home, it is decent and it is free. What it does not give you is an off-site copy, a cloud folder as a destination, or much confidence that the backup is readable, since it does not verify local disks at all.
Ours means the version you purchased keeps working and keeps receiving fixes. Nobody can honestly promise every future feature for a single payment a decade on, and a vendor who does is either going to break that promise or stop developing.
Nothing is deleted. No old version is removed because a license lapsed, and your newest backup still restores on the free tier. Browsing older versions goes back to being a paid feature, and it unlocks for anybody the moment the newest backup cannot deliver.
Related: pricing, Copy Shelter and Time Machine, and the 3-2-1 rule.