Used Scott Airpac

Assuming they're in reasonable condition (expect nicks, scratches, scuffs, etc, but no major gouges), and they come with working valves, I would say that's a good price, especially considering all are still within their 15-year lifespan. That means they can still be hydro-tested, and 1) the user will have a high confidence that it's a safe tank, and 2) they can be filled at commercial shops, if desired. What size are they (as in, are they rated at 30, 45 or 60 minute)?

If new valves are needed, and an SCBA fitting is desired (as opposed to DIN300), one of the members here (Jerry? I can't recall his user name) has posted in the past that he might be able to get a refurbished valve for under $40.
 
Local to me is Bay City, MI. The tanks are 30 minute tanks with valves. The pictures showed scuffs and scratches, stuff you’d expect from used fire equipment. Didn’t look damaged, and I can’t imagine they’d sell anything that is damaged, as a municipality they’d likely scrap them to avoid any possible liability. It looks like they may be 2216PSI, so not useful for a PCP. 
 
I paid around that last year on ebay for a 30 minute tank. I forget exactly, as it was advertised as a 45 minute tank, so I challenged the seller when I received it. I was refunded $25, which made it an OK deal. The tanks you're looking at are newer, so that's even better. If you're shooting a lot, or big bore, a 45-minute or larger tank would be better, but 30-minute tanks are easier to haul around.
 
Cherry pick the newest ones if they cost the same price. Big plus if you find one with a fresh hydro.

Inspect for the nicest condition too.

Sellers do have a liability burden if things happen.

I would ask for them to atleast fill it up that can prove it doesn't leak.

Selling them with no current hydro does sound like they are taking a risk and knowingly being liable too.
 
You could partially fill from a tank but I would not. The high pressure part is the hard part of pumping. Used tanks are not hard to come by but the newest of the tanks the OP described would seem to be worth at least the asking price if they were 4500 psi. I wouldn't pay that much for the oldest ones. I bought an expired 45 minute 4500 psi SCBA tank for under $100 with a valve that works fine. If the pressure limit is that low, I would pass. Ebay is a good place to search for used scba tanks.