I really messed up

There are other options depending on you skill level. Do some research here, dying traction battery’s seem to be quite common lately

 

Before you just glibly start casting criminal aspersions, be aware that you are comparing apple to oranges there. For $800 you get a bunch of old and used battery modules cobbled together using who know what processes, that may last anywhere from a month to a couple of years; whereas for $4,000 you get a brand new set of factory fresh modules installed in your car with a 3 year warranty and your car will have 10 or more worry free years of life, as far as the HV battery goes.

I don't know how recently you got that price of $4,000, but that is a bit high. A more reasonable range would be $2,600 - $3,200 depending on whether they needed to also replace the HV battery ECU. So, you have room to haggle for a better price.

As Skibob said above, there are also other options.

Food for thought?

 

I could not have said it better myself.