Teeth cleaning/pulling

Well I finally got the boy up to date on all his shots and set the appt for his teeth cleaning. But I find myself worrying about the condition  of his teeth and if any of them will have to be pulled. The Vet said they are dirty but nothing else, he didn't really give his mouth a thorough exam.. Two of the back molars on the top right have heavy buildup and the gum is a little red, he also has bad breath. Other then the little bit of red above those teeth the gums look pretty normal with no obvious marks/redness. This would be his first cleaning @ 7yo.

My question- How bad do teeth/gums have to be in order for the vet to feel like they'd need to be pulled not cleaned?

What's the average cost for a tooth removal? Just want to prepare myself if/when it happens.

I haven't had to deal with dental work for my cats--how did it go with getting your kitty's teeth taken care of?  Hope it all went well.