Hmm.
Let's see, here's 14:
1. Automatic transmission (deal killer for me)
2 Unreliable. They're not POS's, but AAA membership is advised because its not a question of if you get towed but when.
3 expensive to fix. notorious electrical issues. You think the price to fix 'em goes down after 20 yrs?
4. I'll wager $9000 is not a bank breaking amount, but unfortunately that's the cheapest part of owning one.
5. 81K is not many miles for a Toyota, but can be a lot for a Jag. remember, not many Jags are used as long term daily drivers. But age is the far bigger enemy for this car, not mileage. it's a 20 yr old New England based British luxury car. Beware of corrosion and component failures due to age.
6. Depreciation: terrible. Don't expect the value to jump suddenly as Jaguar built far too many of them
7. the average age demographic of Jag owners is closer to your parents than you.
8. the 27mpg is misleading, that's the EPA highway rating. It has a tall overdrive gear, just like the corvette, but you'll only get close to that kinda figure if you drive it very conservatively on cruise control. but who drives a car like that as a hypermiler? Don't be surprised to see low to mid teens for MPG.in normal use.
9. All the features, wood dash , etc he's bragging about, were all standard equipment. It even has leather seats (gasp).
10. This is a hardtop, I thought you were a rag-top guy.
11. 300 hp was a big selling point... 20 yrs ago. Now, base model Mustangs have more than that. A "Rocket?" Uh, no. Still it was a fast car back in it's day, but there has been a horsepower war over the last 2 decades that the seller seems to have completely forgotten.
12. "Speed rated" tires? Uh, every tire has a "speed rating". Nice and vague, seller.
13. And probably most importantly, looking at Edmunds.com for his zip code, that appears to be $5100 car. He's seeking $9000. If the seller considers market price "low-balling", and you still want it, I'd suggest waiting him out until he prices it more realistically.
14. XK8's top speed is not 170. The seller is using alternative facts, probably concluding since the speedo goes up to 170, that must be the top speed.

. when it was new, it's top speed was more like in the 150's. Not a slouch, but more like a 350Z. 20 yrs later, I doubt she'd top out that fast even if you had enough real estate to attempt it.
Other than the above I see no reason.

.
Clearly, old XK8's are still sexy looking even after 20 years, (looking a bit like an Aston Martin helps). They're comfortable, luxurious tourers that perform/handle very well...when they run. I freely admit to enjoying the one I test drove long ago (not on track), but the automatic sapped enough fun that I declared I'd never buy one. 15-20 years later, my opinion has not changed despite their becoming so cheap to buy. But that's just my opinion. The ideal situation with any Jaaaaaag is driving it followed by handing the keys back to the owner before something breaks. Hope that helps.