Has the OP owned a Tesla in the past? If not, they have a lot to learn for me to feel comfortable suggesting the idea of buying one. First off, as far as displayed range goes there's the EPA "Rated" (which is typically 5-20% overstated for folks who drive over 70mph) and then there's "Ideal" (no one seems to understand why ideal even exists, but I assume it's the optimized range when driving a constant 40-45mph). Many private sellers and used car dealers will switch the display setting to "ideal" to overstate the range. So you'll want to make sure you're comparing the two vehicles under the same setting.
Secondly, a warranty from Tesla can be worth a whole lot. I bought our 11/13 S85 just shy of 60K miles and had about $10K of warranty work done before 2yrs of ownership which included:
- drive unit
- tpms retrofit
- rear windshield defroster
- HV contactors
- pyro fuse
- HVAC drain hose retrofit
Overall I'm happy with my car even though Supercharging from 20-80% SOC takes twice as long thanks to a crippling software update which I believe was done in the name of safety but I have no proof other than a correlation of events. When I bought the car, I was prepared to drop up to $30K in future upgrades (battery) in hopes that the car will stay on the road for at least another 8-15 years. Since then several design flaws have been discovered; some addressed and others not. I bring this up because it's all part of the "early adopter" experience where Tesla is learning things as we are using the vehicles. If you don't mind setting aside some funds for potential future repairs then yes, there are ways to upgrade the original battery pack. But there are several folks who refuse to own these cars outside of the warranty period.
What's worse is that some sellers might be concealing cars with known battery issues by paying for defeat devices, so you might want to do some research on that too.