Put it this way - it's not cheaper, but it's more affordable.

Say a price of a brand new Tesla is 100k Euro. If you got a loan from a bank to buy it, you might be paying back 1000-2000 euro a month just to pay it back in a few years. That is quite a lot. There are companies however, which let you part-lease or part-hire or however they call it, when you pay roughly 1/2 of the value of the car over 3-4-5 years, but you don't get to keep it at the end. So you might have a brand new Tesla S, for say 400 euro a month - which is very affordable. The only caveat is that you don't get to own the car at the end - but for a lot of people that's not a huge issue.

This is like when your carrier pays for the phone, lets say you pay 10 EUR per month for a mid class phone and 20 EUR per month for a premium phone. Looks like a small difference (+ a "price" for the phone)

If you buy both without a carrier, you might pay 400 EUR for the mid class phone and 800 EUR for the premium phone. The price difference no looks huge.

(The difference in acucmulated prices is the "buying" price of the phone)