I was conflicted on getting a post bacc degree since I double majored in Creative Writing and Studio Art, only receiving a BA. I came from an amazing undergraduate degree (private liberal arts) so my professors were very positive that I was ready for a masters, based on my work ethic, serious determination, and maturity as a student. I also took time between degrees to further push my portfolio on my own. I do not recommend the post bac degree to anyone who had a BA or BFA in studio arts, but I do for anyone who is unfamiliar with art history, got a different undergraduate degree, or is just considering one year to continue courses for personal enjoyment. You receive a lot of classes, a huge year of studying and practicing, and you could get super burned out. Halfway into my MFA degree I realized I wanted a break! MFA programs can take 3 years. Mine took 2.5. The potential you could create your portfolio by just spending some time, independently, focusing on your craft and becoming immersed in the art world-visiting museums, reading, and galleries, this is most important. Not spending 20k on something you don't need to prep for masters.
If you are on the west coast of US, or anywhere, I will say that our post bacc at my graduate school is amazing. They really show you what grad school will be like and what you want to do. They immerse you the POrtland, Oregon culture as well. Oregon College of Art and Craft. I would have done that if I had an infinite supply of wealth. http://ocac.edu