"900 pounds on fishing? That's a lot of money!"
Only if you haven't got it, but if you do Fish as your main hobby and don't spend on a habit, such as smoking then it isn't.
I used to Fish, my ex had thousands worth of gear, I used to buy items as presents, often £200+ at a time, it is worth buying good gear.
My DD tries to tell me what I shouldn't be spending on camping gear, whilst she smokes, it's different with a partner, but if you go on the premise if having equal spends, it may balance out, tbh.
Plus, your DH is doing it as a family event, I don't see a problem, tbh, except for the lack of communication, but can you be controlling?
I see a lot of partners try to tell their other halves what spending limits they should put on their interests, if it doesn't impact on the family, you need your own hobbies. If you aren't into hobbies, you don't get it.
If he enjoys being online, he may if offered to research something for someone, or it has been automatically linked.