Right now we're close to "low income," and my husband is a tenured professor at a well-respected university. It's amazing how having four children *and* living in an expensive location can really change your perspective on income needs.
I voted 50,000. At this income level, all extracurricular activities would be out of the question (or subsidized via scholarships), we'd have to move to a less-expensive part of the area, our annual trip to visit family back east would be eliminated, and we'd really have to limit our driving to essentials to save gas money.
At our current income, we're able to do a few extracurriculars, make a vacation trip to visit family, keep our home in a gorgeous part of the country, contribute to the church offering basket, and take weekend camping trips every few months.
BUT: we have a strict food budget, buy all of our clothing/household goods used, heavily ration our water use, and rarely splurge for "extras" like dinner out or new toy/books.