It’s 4% of the adjusted lease balance, which is essentially your current lease payoff not including any of the taxes or fees.
So if your payoff right now would be roughly $75k before taxes/fees then the all-in payoff would look something like:
$75k payoff
$3k early termination fee (4% x $75k)
$150 purchase fee (or whatever is in your contract)
$XXX sales tax (based on your local tax rate)
The sum of those things is what you will owe to buyout the car early.