The max I have spent, 3k, the most I would spend, ?? I think it varies by designer and bag at least for me. I weigh how much use it will see, how versatile it is, and if it fits in my wardrobe.
Someday I hope to own a Birkin so I am sure that is the most I will ever spend on a bag but for now I buy what I like and can afford (Birkin is still way out of my $$ range)