Applied to 41 schools (cycle number 3! woohoo!)
Primaries: $1560
Secondaries (41): $3635 - jeez.
Interviews (6): ~$2200
Second Looks (1): ~$200
Total + random costs: ~$8000
I got lucky and was able to secure two of my interviews out in NY during the same week--otherwise travel costs would have been even more going back and forth from CA. Plus I signed up for a Venture card earlier in the year and started charging EVERYTHING on it--it earned me enough miles to redeem a few smaller flights and miscellaneous travel costs (lodging, shuttle, etc)--any little thing helps. If you're applying soon, get yourself a rewards card now that has some sort of early signing bonus--usually that bonus is enough for a free roundtrip flight.
Most of my flights were cross-country, so I made it a point to arrive a day before my interview, and leave the day of (sometimes early the next morning). ALWAYS look for student hosting!! I loved the security of speaking with students before my interview, being close to the school, and not having to sort out traveling between a hotel and the school, dealing with parking, transportation, etc. I managed to secure hosting at all my interviews, even using SDN to get in touch with an unofficial hosting program at UIC! This saved me a ton of money
Other tips: Airbnb is interesting if you can find a location close to your interview. For my trip to Chicago, I stayed with a host before my interview, but the earliest flight back wasn't until the next morning. I managed to book a cheap Airbnb room close to the airport/the L--saved me having to go for a full-on hotel for the night.
I agree with applying broadly/smartly. Beyond how taxing it is mentally, this process is expensive. My parents helped pay for my first cycle, but I've paid through 2 cycles myself and it's a huge money suck. Be smart and do it once