Haha! Yup. I also don't negotiate. Ever!
I can pick up on the cheapskates in an instant. I also know from
experience that the cheapskates will question your work, agonize
over any unforeseen surprises, and be overall pains in the asses
of all who work for them.
You took a low offer, and then after you start they want to eat up
what little profit you have on "chatter" about the job. Fuck off!
I hope to never be that desperate again.