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.