The Garmin Edge 520 is probably the cheapest and best bike computer on the market for what it sounds like you want it to do.

Garmin Edge 25 about $120 retail now. Will do all you want.
You can find older Garmin 500 here in classified for under $100 often.

check out the Garmin 130. It's new and does a lot of what the 520 does.

This.

The 25 is nice, and tiny, but it's quite limited in what it can display (only 2 screens, one with 3 items and one with two). Plus it can't do power if you ever go that way.

The 500 is too old and not supported any more.

The 500 may be old, but it can usually be found for about $50-75 in the ST classifieds. It will do everything the OP is looking for and more. By "not supported" I assume you mean Garmin won't fix a 500 if you try to send it in for repairs (that would be kind of silly, because I would just buy another one for $50).

The 500 is certainly still "supported" in that you can still upload activities to Connect (albeit not via wifi or BT but with a cable).

I use the same 500 almost daily on two different bikes. I don't need mapping, touch screen, and text messages. I just want to see my ride data. The biggest drawback for me is that the 500 lacks the option to store multiple bike profiles. Meaning I have spend an extra 10 seconds pairing to the other PM when switching the head unit between road and tri bike...but who cares, it's 10 seconds while slipping my shoes on or buckling my helmet strap.

I suppose someday I'll get a newer, fancier head unit. At present, the only motivation for me to upgrade would be if someone stole my 500 in transition (which of course will never happen) or for compatabilty with the Garmin rear radar (which I don't yet have). Until then, I'll keep rocking my old 500 and use the $300 I'd spend on a new head unit to buy something that will actually make me go faster.

I made my suggestion based on owning a 500 myself. I'm not upgrading it unless it dies either, but it wouldn't be with another 500.
The USB port is flaky and the rubber seal never closes well.
No Bluetooth upload is annoying.
No GLONASS, so finding satellites takes much longer than new devices.
It _does_ have multiple bike profiles, but you have to dig through the menus to find them, and the functionality is limited as you said. I never bother.
They are known for crashing or locking up, and as I said Garmin won't be providing any more firmware updates (though Garmin Express keeps popping up telling me there is one...)
The battery life always says 100%...

The 130 is basically a re-done 500 in terms of functionality and design, but with all the modern conveniences.

I've just never had any newer device and proabably don't know what I'm missing. But, it sounds like the 130 will be my new head unit if my 500 ever dies. I'm secretly hoping someone actually does steal the damn thing so I have an excuse to buy a new head unit and the radar.