Well, I STOLE the load center, twice. Bought a second one just to get more 3 phase circuit breakers. They are valuable, but also not many looking for one. That means you can find one cheap if you scrounge. I won't guess where you'd end up.
"The Kid" got a 20 hp 3 phase motor for $100. That's a pretty good deal. I gave him the 5hp. Cheapest way to get a 5 is to buy it on a piece of equipment.
With any luck you'll get the motor contactor for the 5 with the above deal. Other wise maybe $20 on eBay. A 20hp might cost ya, I'll guess $75 on eBay.
You'll need a box to put it in, stop and start push buttons, start caps, run caps, relays, time delay relays, wire, terminals etc. This stuff can hit a couple hundred unless you scrounge well.
This unit was designed to be deluxe and last the kid a lifetime. Its possible to go real cheap with a single motor, no balancing caps, just a push button to hold in the start cap, skip the load center, yada yada
Karl