Trevor here, creator of the Spanish Bible app.

IkmoIkmo got this spot on in his/her comment.

Biggest two mistakes people are making in this thread:

1. $100k was revenue, not profit.

2. I get capital gains rates on the sale, versus ordinary income rates.

(If you didn't know about #2 you should probably sign up for my accounting and tax course for freelancers and entrepreneurs: http://trevormckendrick.com/accounting-course-for-entreprene...)