There's a company that saves its customers about $6 for every $1 it makes, and investors just valued it at $60 billion. Plenty of the businesses using it never pay it a dime, because the basic version is free. The company is Ramp, the corporate card and expense software. Eric Glyman and Karim Atiyeh started it in 2019 with a mission they wrote on a Post-it, save companies time and money. This week they posted the receipts. By Ramp's count, its 85,000 customers save over $1 billion a month.…