Re: replacing a battery pack is fairly easy
Not if Emperor Elon (the last) gets his way. He wants batteries to be part of the structure of the vehicle. That makes replacing them an absolute nightmare. I don't think it will be too long before your lovely tesla is written off after a minor prang because the cost of repair is so prohibitive. Oh... and it can only be done at a Tesla service centre who love to take months to get even simple parts from the Elon Mothership.
Even skateboard chassis cars like the ID series need properly trained people to work on the main battery. 400V/800V/1000V and a lot of Amps are not to be sneezed at nor taken lightly.
As for the service costs of that Tesla. Perhaps that included a replacement Battery? Early Tesla's were like early Nissan Leaf's in that their battery degrades pretty quickly. Battery tech has moved on since those days (pre 2016/17)
Most Battery makers are now predicting 1,000,000 miles on a battery. That means you won't have to replace it in the lifetime of the car.
Makers like Kia/Hyundai have 7 year warranty on the whole car including the battery.