Super dwarf females get around 8ft. Males smaller. Whether or not the price is good depends on the age/size. If it's a hatchling, I'd look elsewhere. I'd also make 100% sure that it's actually a super dwarf. Other "dwarf" get significantly larger, and super dwarf crosses can vary a lot in size. If you really want one, I'd go to a respected breeder and not purchase something off Craigslist.

The size of an SD retic is fairly comparable to that of a large common boa, but the attitude is much different. SD retics have the same strong feeding response as their larger relatives. They're also much more high-strung, and require more work than a boa. They're fantastic snakes and I love them, but I'd say there a step up from boas.