<human>: Hi there,
Sorry for the long post.

I initially posted this in /r/askcarsales, but some nice soul out there recommended me to post it here as well to get more legally correct advice. Although I already got some great responses there, I thought it would be ok to get you guys's word on it as well.

I sold my used 98 corolla 3+ weeks ago to an old couple. I had priced it higher than KBB value because craigslist loves to negotiate. But this couple never bothered me with negotiation and bought it at the advertised price. Fast forward to 3 weeks during which they drove it around without issues, they get new tires and were recommended to get alignment done. The mechanic at alignment gave them bunch of stuff that needs to be fixed/repaired. Repair cost estimate is 1900 according to them. They were also told that wheels were in pretty bad shape and should be replaced as well. Now they are all over me to pay for the repair cost or atleast the half of it, accusing me that I knew about all of the repairs that would be required. I feel bad for them really, so I offered them 400 dollars, but they have put the limit on 600 and if I don't pay them, they are planning to sue me. Most bothersome part is the accusation of cheating. If they hadn't accused me and took me on a guilt trip I might have actually already refunded them 600, but who's to assure me that they won't threaten me again with something else in few days ? Also, I didn't do a single thing outside the moral/ethical or legal code. Please also note that the husband asked me if he could write 1200 as the purchase price on the title to save on some taxes. The actual sale price is double of that.
Any suggestions ? Advice ? I know I don't owe her a thing, but I seriously don't have the energy to deal with court case and worry about it everyday until it actually happens.
Thanks guys!

Give me the gist of the text in a nutshell
<bot>: Sold a 1998 Corolla ~4 weeks ago in California, now buyer wants refund/repair cost or threatening to sue.