I see 55 gal all the time but I don't like how little depth they have.
On rare occasions a 65 till turn up. I love 65 gal tanks.. 18" deep, 24" tall.. Lots of room to work with.
10 Gal all day long but as you noted they want as much or more than new for them.
They had a Oceanic 30 cube I wanted but not for $50.. That violates my $1 pr gallon rule on used tanks. Someone snagged it before it hit 1/2 off week.