When I got my TiVo a few years ago, you could buy a lifetime subscription. I think it was about $300, which seemed pretty reasonable. I've had the unit for almost 4 years so I've definitely broken even on it.

They still seem to offer a lifetime plan, but now it costs $600. That's a bit harder to justify.

What recurring service are you notionally paying for every month??

I think the channel guide data. Without it, the TiVo doesn't know when to record what. $10 still seems very pricey for that though.

Tivo Roamio OTA ($49.99) will let you do this if you never activate the subscription. You can use the tuner and buffer the broadcast stream.

This never came up in my research (although I was biased against Tivo), but I just checked and it said:

"$14.99 Monthly service with 1-year commitment"

Do you (or anyone else) know if the Tivo will work without an internet connection?

Yes, it will work without an internet connection.

I bought a Roamio OTA for my mother-in-law, who has no internet. I set it up at my place (it usually wants to upgrade to latest firmware over wifi when you unbox it), scanned for the OTA channels, then I took it to her place and wired it up.

The operation without monthly activation is bare-bones. I mean, you don't even get channel or station names. But you can tune to prescanned OTA channels and watch tv and pause it live.