What to gift someone who's obsessed with cooking?

If he's constantly experimenting, look for kitchen gadgets that are in his blind spots - like a professional-grade immersion blender if he doesn't have one, or a good kitchen timer with multiple programs. I think people obsessed with cooking often don't treat themselves to these little things, and then they're really grateful when someone gets them one. It fits easily in your budget, and it actually makes life in the kitchen easier, rather than just sitting pretty on a shelf.

I'll partly disagree with the previous answers here. Sure, tools matter, but only if you're actually confident he doesn't already have them. A knife or scales - that's a very personal choice, and someone who cooks seriously has definitely already picked out the equipment that suits his style. Give him the wrong thing and he'll politely use it, then stick it on a shelf and forget about it.

It's way safer and more interesting to give something that broadens his horizons instead of duplicating tools he might already have. For example, a membership to cooking classes (online or in-person, depending on where he lives), a nice set of unusual spices and pasta from a trusted supplier, or even a culinary tour package. If his tastes run milder, you could go with a beautiful book on food history or recipes from a famous chef in a nice edition - something about ideas, not technique.

Another option within your budget is an electric kettle with precise temperature control, if he doesn't have one. Sounds modest, but home cooks use water all the time: brewing tea, steaming, checking tempering. Models like Gooseneck look professional and actually do the job. The key thing is to ask your brother casually beforehand what he'd like to improve in his kitchen or what he's been looking for lately. Even a hint will help you hit the mark.