That's not really an unreasonable price for a Jack in the Box that needs some work. If there are major functional issues, or if the backglass is flaking, or it has significant playfield wear, $500 might even be a little too high.
Also, a lot of pinheads are terrible photographers, or just lazy. A single picture doesn't necessarily mean there's anything wrong. Maybe the guy just isn't a photographer.

It does cost money to have a pinball expert fix your game. Many charge around $100 for the first hour, and $60 or $70 per hour after that. He might not have wanted to spend that much to fix it.
Also, I noticed that the Flipper Room only has one EM game, Doodle Bug. Maybe their tech does not know EMs and couldn't fix Jumping Jack. All kinds of things could be going on here...
You can fix it for FREE by reading Pinside and asking us how! We'll be happy to help!!!

It might be worth it to take a ride out there and have a look at it yourself if it's not too far away. The Flipper Room looks like a decent arcade, and you might come home with a cheap Jack in the Box!

Here's the Flipper Room's current lineup...looks great! I'd head out there just to check out the games... Good luck!

Aerosmith-Pro (Stern, 2017)
Alice Cooper's Nightmare Castle (Spooky Pinball, 2018)
Alien (Pinball Brothers, 2021)
Avengers Infinity Quest-Pro (Stern, 2020)
Baby Pac-Man (Bally 1980)
Big Lebowski, The (Dutch Pinball 2016)
Centaur (Bally, 1981)
Deadpool- Pro (Stern, 2018)
Doodle Bug (Williams, 1971)
Elvira's House of Horros (Stern, 2019)
Flash Gordon (Bally, 1981)
Flintstones, The (Williams, 1993)
Gladiators (Gottlieb, 1993)
Indiana Jones: The Pinball Adventure (Williams, 1993)
Joker Poker (Gottlieb, 1978)
Last Action Hero (Data East, 1993)
Mandalorian (Stern, 2021)
Paragon (Bally, 1979)
Rick & Morty (Spooky Pinball, 2020)
Space Invaders (Bally, 1979)
Star Wars (Data East, 1992)
Super Mario Bros. Mushroom World (Gottlieb, 1992)
Teenage Mutant Ninja Turtles-PRO (Stern, 2020)
Total Nuclear Annihilation (Spooky, 2017)
Twister (Sega, 1996)
TX Sector (Gottlieb, (1988)
Waterworld (Gottlieb, 1995)
Willy Wonka and The Chocolate Factory (JJP, 2019)

Hmm, I can see why you would wonder about that.
Part of it could be that there is less demand in that area for EMs in general, but I would guess that the local pinheads looked at it already and decided it was overpriced for its condition.
I'd put that one on the back burner for now! Nice clean games are out there, and it's worth paying a bit more to get one from someone with a good reputation as a seller and pinhead. Patience always pays off in the pinball world.