As aggravating of a non-answer as this is, it depends/YMMV. Some folks take 100s of dollars to spend on souvenirs. Others buy 1 magnet and call it good. I think if you sit down and think of the usual fare of souvenirs and what you might like, you can then determine price points and budget. For my kids, they have their own money and I do not police its spending. From us, they get 1 tshirt, 1 hat (if desired), and 1 souvenir of choice which cannot be more than $40. All of that combined tells me I'm likely looking at $75-100 per kid. For us, we get 1 ornament, 1 magnet (if desired -- we already have WDW magnets so likely will pass), and 1 item of clothing if we see something we like. And I'll probably add a bracelet to that. That has worked well and kept us from getting too much stuff. Occasionally we might get another small item, like a matchbox type car, but usually that's it.