Was watching Rods 'n Wheels on Sky and the guys put an EV West battery conversion into a Beetle. Seemed to fly down the drag strip but a figure of $20k was mentioned for the conversion.... probably the cost of a 200 mile mains lead ;-))
I found instructions on how to do it yourself with a bug a few years back, they were fron the 1980s I believe, and relied on a buttload of lead acids. Looked cool but yeah, expensive, time consuming and a pretty severe limitation on how you use your car.