Just got an email from a co-worker, this morning he crossed the 10,000 mile commuting mark since he started tracking in 2009. He doesn't ride every single day or in the winter, but averages 2-3 days per week 8 months out of the year. Good for him for getting out and doing it.
He showed me his detailed spreadsheet where he tracks everything. He's figured out how many miles he rode instead of driving, his per-mile expenses for driving broken down by year, and all of his bicycle related expenses. I found it amusing that after seven years he's only ahead $157.
Thankfully there are other benefits to cycling other than money savings!