Ive got very limited experience with Sabatti.. Ive only shot a couple, and have never owned one..
I do think they get a pretty bad rap overall because of the old Cabelas run (they earned it).. but.. that appears to be a one off sort of situation.. outside of the cabelas run that went bad, I havent heard of any systemic problems with them with any of their other doubles..
$7K seems to be a fair price depending on the amount of use and condition the gun is in... Ive definitely seen them go cheaper (in the high $5000's and low to mid $6000's).. but Ive also seen guys try to get higher prices out of them (seen them listed on GB and other places in the $8-$9K range for used)..
Youre definitely not buying an "investment" gun like would would be with some german or british guns.. but youre also not paying german or british prices..
The RMR and the associated work done to mount it properly bring a little bit of additional value I think (again, youre not buying an investment gun.. youre buying a hunting/shooter.. and a lot of people hunting with doubles are moving to red dots these days).. I paid about $500 for JJ to create a mount for my wifes Chapuis double so that it would take an RMR.. and you figure a 1 MOA Type 2 RMR is about $800 these days (new in the box)..
I think a lot of guys dip their toe in the water with doubles by buying something like a Sabatti first.. its not cheap.. but its definitely among the most affordable ways to test things out and see if youre going to like a double or not.. and.. assuming you want to upgrade to something else later, my guess is you'd probably get most of your money (maybe all?) back out of the sabatti if you chose to sell it...
Were I in the market for a low cost, entry level double... I'd probably at least consider a $7K sabatti..
and.. who knows how motivated the seller is to let it go... I'd probably offer him $6500 and see if he'd take it if I really liked the rifle and I thought it was in decent shape, etc..
I would definitely recommend getting the serial number and confirming that it is either NOT one of the bad cabelas guns.. or if it is, that its one of the cabelas guns that Ken Owen worked on prior to passing... if Ken worked on the gun, its honestly probably a better shooter than anything coming off the sabatti assembly line right now..
if you ever want or need to sell the gun, being able to confirm its not a cabelas gun, or is a Ken Owen "fixed" gun will make things much, much easier for you..