If I had to choose between my snakes and could only keep one it would be my boa. They have great personalities and are just fun to keep (and don't hide all day).
A normal girl that size would most like likely go for around $200. The issue is that there are tons of normals available to adopt and pick up on the cheap on Craigslist. If you have her set up properly you will probably find her a very rewarding snake to keep.
She should shed for you in a few days and will be much lighter and maybe have some peach and pink colors showing on her sides and belly. Very pretty.
Some people feed every week and many boa keepers slow grow them. Adults can be fed weekly, but some feed every 14-21 days and have big, gorgeous boas to show for it.