I've purchased two private party Tesla's. One with ESA and one without. I think it depends on how sweet the deal is. On a 50k used car you are talking about 4k just in sales taxes + reg (CA) that I saved on (and annual reg is based on valuation, so $$$cha-ching$$!), with that extra saving I could have purchased the ESA, but chose to take a chance. We will see if it pans out. Being that the battery and motor are covered to 100k, $4200 goes a long way to fixing a non ESA car. I personally don't think you will get your money out of it. Sell it before the 50k and let them decide. BTW, I just had my non ESA P85 door handle malfunction and break which tesla quoted $900 to repair, so I'm still ahead! (actually I'm way ahead because I'm going to fix it myself for $150)