Items and potential issues that I typically check for when advising someone on buying a 780:

-Rust hiding under the rear fixed side windows (under the trim).
-Sunroom leaking water (usually caused from the doors being slammed with the windows rolled all the way up on a hot day and momentarily overpressurizing the cabin)
-Knock sensors on the V6 (the pair usually go bad around 150,000 miles, cost of $100 each not including installation and usually a $250 deduction on the price of the car).
-Transmission tailshaft bushing wear ($20 in parts, two hours labor) and other possible driveshaft issues.
-Turbo charger oil leakage issues which are sometimes fixable by cleaning the Oil Trap next to the starter (not to be confused with the Flame Trap on a N/A engine). -other times caused by worn oil seals on the Turbo (a $300 to $800 deduction from the price if the Turbo merits replacement with a used or new one)
-Compression Check (my desired numbers): 185 to 210 expected for B280 engines, 170 to 190 expected for a B230 Turbo, and 175 to 200 expected for a N/A B230. The Green book Pass/Fail spec is 145 psi or no more than 10% difference between cylinders, but I'm wary of anything below 165 psi.


When I bought my pair of 780s about 3 to 4 years ago, the prices were as follows (all values in USD unless otherwise noted):

$9,000 to $10,000 - KBB in Excellent condition, V6 or Turbo, from 88-90.
$900 to $2,000 - final eBay prices for V6 cars in poor to good condition.
$1,500 to $4,000 - final ebay prices for Turbo cars in moderate to excellent condition.

I don't know why the prices were so low a few years ago, but it may have been in part due to some economic recession issues that we've mostly recovered from (prices were down on other classic cars too at that time, you could buy a DeLorean for $4k to $7k on eBay). Anyways, usually the value of a car goes down with age, but just looking at the numbers now I'd say the value of a 780 has been going up recently. I've been helping a gentleman out via email who just paid $5000 Canadian for a rust-free V6 780 (in Canada) with about 100,000 miles on it and I was a bit suprised at how much it and others like it are selling for.

I checked out the one you were referencing on eBay, and based on the bidding history and the fact that the reserve is not yet met, I'd say you may not win this auction unless you're willing to spend a lot of money. Be patient, and be willing to trade off on certain items for a much reduced price. A 780 Air Dam is a coveted item, but you could get the major parts from your Volvo dealer for $350 to $500 and paint & install them yourself. Also, I will not advise anybody to buy a turbocharged engine or a PRV-6 without having it compression tested before hand. I got bit once before when advising a friend to buy an '89 740T, which ended up having major cylinder wear due to neglected oil changes and a warped engine head (we had to replace the head & the head gasket).

One suggestion for acquiring 780 parts cheaply is to do some salvage yard shopping while traveling or on vacation. I'll run a few searchs through http://www.car-part.com/ for hoods/trunks/doors for a 780 using the zip codes of where I'm going to be while traveling. The search engine returns lists of salvage yards and their phone numbers that have the desired 780 parts, and I'll call them and inquire about the car and ask about it. If it sounds promising, I'll ask about stopping in to see the car in person. I'll pick over the car for items that I'm in need of or expect to need later, and then offer the salvage yard a lump sum for a pile of parts. (example: I paid a yard $220 for a set of four 780 wheels & tires, a tail light, AMM, the radios & amps, fuel door, the remaining half of an Air Dam, and a ton of exterior trim. Both the salvage yard and I thought we were getting a good deal.)

If you're willing to spend some time turning wrenches and doing a bit of research, you can pick up a decent 780 and bring it up to Excellent conditon over the course of a year.

God bless and enjoy the drive.
Fitz Fitzgerald.
--
'87 Blue 240 Wagon, 290k miles.
'87 Silver 240 Wagon, 410k miles (wife's car).
'88 Black 780, PRV-6, 150k miles.
'89 Black 780, Turbo-4, 94k miles (accident vehicle, might be restored).