Yes, it's cheaper to buy it now. I said that.
But, it's a much better deal for you. If someone buys early (34K) you get the money earlier and have more time to invest it. You're not out anything for a while because they have to (right?) go through the OEM until it's expired. And, they don't get the benefit of a full 75K additional warranty because they bought early and saved $500 (I ran a comparison on one with 34K and 50K). So, they "save" $500 by buying now and gave up 16k miles of coverage.
No you do not have to go through the OEM until its expired. You absolutely can use X-Care to cover service costs but X-Care has a $100 deductible per visit so it wouldn't make too much sense to do so since you would already be under warranty. However, you can use some of the benefits of X-Care...for instance, if your vehicle had a breakdown and you are more than 100 miles away from home, you can take advantage of Trip Interruption with X-Care while your car is being fixed by Tesla. We would cover lodging and meals up to a certain amount. These benefits that are not offered by Tesla but are by X-Care are at your disposal at any time.
Tesla offers this same cost benefit to early purchasers. If you purchase the ESA within 180 days of initial delivery, the cost is $4,250. If you purchase after 180 days of initial delivery, then its $4,750. This is pretty normal across the board.
Extended Service Agreement