How many GB left on 256 Gig model after OS?

Question in the subject. I'm thinking about buying the 13" airbook, current gen, mostly to run Logic Pro and play around Final Cut Pro. Curious how much memory is left after initial OS install (from factory) and after installing both of those and possibly Live. I wouldn't be working with huge video files or adding tons of music files but eyeing that $200 upgrade for 256>512 GB. I'm sure most will say it's worth it but when $200 is more than 20% of the purchase price I gotta do my due dilegence.

Thanks for the feedback.