Ive been a member over at http://www.motoredbikes.com
for about 4 years now and yes, motorized bicycles are growing by tens of thousands.
There are 15,378 Members and probably 7000 members have built at least 4 to 20 bikes. There are ruffly 7 choices for kits for installation ranging from 169.00 to 700.00. And yes, you get what you pay for. There are probably 60 builders like me that build most bkes from scratch without a kit. Here are a few in the last 3 years.