It really depends on how cheaply you can get a complete motor or just the parts. I paid around $300 for cylinders and head. $20 for the PV controller, $20 for the PV servo, 100 for the CDI, $150 for startor and flywheel, $30 for the harness, and around $20 for the regulator. $150 for pistons.
I paid too much for some of my stuff, but it could probably be done for around $800 if you know someone that can make you some flanges.