How much do passports cost? We need some just to go to Algodones.

All passports are through the U.S. State Department. The USPS just provides the paperwork and pictures. Check the State Department website for information. https://travel.state.gov/content/travel/en/passports.html

Depends, if you just want the card or the booklet or both

Cost was $65 dollars for the card last time I took someone there, and was around $110 to renew my book.