I would say closer to $10K for the motor.
I priced out a buggy last week. If I provided 100% of the driveline, the cost was still north of $20K. The quote is a PDF and I can't break out the options but it's easy to wrap up $1000 in seats and harness's, then consider fuel cell, floor, outer skins, $1200 in steering, etc. Dont' forget aftermarket pedal assemblies. And guess what, no one has added in the cost of wheels and tires.
GLFWDA member since 1979.
Member Southern Michigan Rock Crawlers.