If he likes beer .....
So every year here, my friends and I do an advent calendar for our hubbies of craft beer.
That is my main gift for my hubby really - because he doesn't drink beer every night, and he will have the guys over for some to sample (you will find the funniest ones out there with weirdo names), and it's just enjoyable.
To make it more affordable, you can totally mix in some regular beers. We do that, otherwise it does get pricey. You can specialty wrap the craft beer in some fancy tissue.
So they have those wine boxes and we just fill those using some packing supplies and some shredded packing stuff (I think it's shredded paper?) in the bottom because the bottles/cans are not as tall as bottles. We kind of altered the boxes to suit our needs. Then we wrapped them in paper to make festive.
They enjoy reaching in every evening after work to pull out a 'surprise' new craft beer to try or even a regular one at end of day. I bet your son would enjoy one after long day at work this summer.
We also have those flight paddles (probably saying that wrong) which are these wooden paddle things with about 4 little glasses on it for sampling different beers. You could give him one of those too - if he's into craft beers.
We do a strong and clip pictures on for birthdays like a clothesline. Everyone likes that. Do a big 3-0 in the middle.