FWIW, I did a London-Amsterdam-Paris with 2 friends in 1990 and the $100/day still wasn't quite enough even then. Had to do a Visa cash advance via ATM in Paris (my first ever of that sort) to avoid having to ask for a short-term loan. Have gotten better at planning and having back-ups since.

A determined person might still be able to do it, but it wouldn't be much fun. Maybe u could bring a tent and pretend you're starting an Occupy movement, and also go on a fast (er, hunger strike) to underscore that.