I would not recommend anyone apply before they have access to $5,000 (be it credit card, cash, parents, etc), so that you aren't scrambling to come up with money in the middle of the cycle. It may not cost that much, but you want to just apply once so be prepared for everything.
I spent a lot. Not going to do the math, but probably over $7K. I worked a year to save ~$13,000 for applications, so I didn't worry about any costs. I went on 11 interviews, 5 of which required flying (I fly anywhere that is more than 6 hrs away by bus). One interview cost me over $700 because it was in the middle of nowhere....they waitlisted me and was the only school that rejected me post-II too -_- I also stayed for a few days in hotels every time I went to a cool new city.
Edit: if you get lucky, you can interview at your top choice at the beginning. My top choices were interviews #9 and 11. Could've saved a lot if they were earlier