I'm sure you can come to an independent consulting arrangement that will prove mutually beneficial. One way or the other they're going to pay stupid tax for being incompetent.

Wish them good luck.

Tell them that would technically be a breach of your nondiscolsure agreement since you're not an employee anymore. They would have to rehire you at your choice of the highest fee possible.

I had a former employer do this i tried to help transition my users from to another colleague when i was leaving. Instead they fired me the second i handed in my two weeks notice, wiping my data instantly. When shit came crashing down, they asked if I still had my data and scripts. I quoted $350/hr with a minimum of 100 hours. The expletives they yelled were delicious, especially since i wrote all the scripts my colleagues relied on and that caused productivity to shoot up 1000% after i started there a year prior. I work for a better company, who ironically services them. The shit show i hear as an aftermath is hilariously bad as they shot themselves in the foot. Recruiters keep contacting me saying they have 10 positions open to perform the job, and when i worked there, 3 of us were able to manage everything ourselves using my improvements. So yeah, feel free to gouge for that data access. **** ‘em!