I've spent... oh, I think I calculated it to be $1800 last time I checked which seems like a silly amount for a tiny metallic object that can barely eek out 30 mph. Still, the car costed me at least $1700 per year just to own and costed me an average $1500 more just to run(including the average crash rate cost calculations, tickets and gas costs, winterization, oil changes, etc.) and at least $1000/year more in depreciation(Let's see... Owned it for two years and sold the car for $2000 less than I initially paid for. Sounds about right!), so I can positively say that my ebike has saved me a bundle of cash as a car replacement thus far. Also, the car seemed to encourage "going out to eat" and other secondary costs that I can't quite directly compare(Like spontaneous trips across the state where I spent money to enjoy a con or just to check out a campus.), so I'd put an estimate on my annual car costs at 1700+1500= 3200 minimum with at least $4000 which includes depreciation(Compare the average annual cost for owning a car is 7800 according to
http://www.boston.com/cars/news/articles/2006/04/23/annual_car_cost_hits_7834/, and my depreciation was about 3000 less, so my figure is probably "about accurate"). Now, my total foray into electric vehicles... hmmmm... let's make that $2300 since last May.

Scooter($70)+upgrades($80)+motor($100)+controller($200)+a123s($230) = $680 more.
I've also become healthier since getting rid of the car which seems to have magically made me avoid the "<insert family's last name>'s curse" which is basically the belly-fattening of males as they enter into their 20s in my extended family's lineage. I really have to wonder what the total impact on my health-care costs will be if I didn't replace the car. I'd probably still get fatter but, then again, I wonder if the bike might be causing irreparable harm to my back which sounds like it'd be costlier than a little fattening. In that regard, I'm planning on eventually changing to a "townie" set up which would help out in the posture department. I might even add a backing to my seat like the kind a recumbent has, haha.
By the ways, $2000 can get you some awesome batteries and range. I think ping is asking for $/wh now for his 3c batteries, so 2000 can get you 2 kwH = 6 kW continuous and 10 kW, 20 second "bursts". That's some serious range and power for an ebike - Even at a ridiculous estimate of 40 wH / mi. (Possible if you're cruising at 33-40 mph), you'd have to truck 50 miles to deplete it. But, I'd have to add my own electronics to monitor the battery since he doesn't make packs of that size and I trust my own electronics more since I understand them and I'd know "what's up" with my cells instead of having these disastrous mysterious failures. On the other hand, I'd say Headway's cells are a pretty damn good deal at roughly .66/wH in bulk so you could get ~ 3 kwh = 12 kW continuous(At my suggestion of 4C continuous) which can get you 75 mph+ speeds and a 75 mile @ 33-40mph range. That's sounding really practical! If the pack lasts you for 5 years as far as your needs go, that's only $400 / year as opposed to the average $500 people pay *just* for gas (on a motorcycle, estimating. Even more if you compare it to replacing a car).