I wouldn't say you "need" custom footbeds. Lots of people have success with generic footbeds and I don't see why you wouldn't consider those as the first option. Sure they're awesome, but to say they're absolutely necessary seems a bit over the top.
I'll also toss my hat in the ring for the try not to have a budget argument. I know that's not a very understanding thing to say, but the value of a good fitting boot is paramount. Just be honest with your bootfitter and I'm sure they can help you find something that works. It's amazing what an awesome fitter can do with $60 of stretching and a simple heat mold. I've seen horrible boot fittings fixed by great fitters later on. Not ideal, but you get the idea. There are options and they'll help you.
I'm not a bootfitter by the way. Just speaking from good and bad experiences of the past.
Slope Style Ski Shop, Main Street Breckenridge