Birthday Gift for Boyfriend?

Funny stuff? He might prefer something useful

Whiskey / whiskey rocks, cologne, wine tasting, nice knife (either hunting or a high-end kitchen knife), record player, some sort of subscription if he's into that, etc.

https://www.hermes.com/us/en/product/snowpark-tie-H606119Tv20/

Headphones are always nice. Another pair of sport headphones or oversize headphones are great. You can get some for super cheap on Amazon or spend some $$$ on designer audiophile ones or anything in between. There are a lot of choices out there. 

how about a sex slave to be punished?

i just got a pair of Bose noise cancelling headphones for $160...they are awesome and very comfy

If he likes to cook, then a cool kitchen gadget / countertop appliance

if he likes guns, then you could goto a gunshow in Pennsylvania and buy a cheap gun and some ammo to go sport shooting

(or a bow and arrow)

If you don't have bedroom toys (ropes to tie up, and other BDSM stuff...plus the sexy model to go with them) that would always be a hit

honestly...you know him...what are some things he's interested in?

Sex

As some have said above, give him SEX... as much as he wants.

I want a proper work/gaming station. A really nice PC would be the best gift I could get. Should run 5-10k, depending on how much you love (or don't love) him.

A car would be another great gift. Maybe get him a BMW M3.

At the end of the day, I'm going to assume he loves you and you love him. So get him something thoughtful, or don't even get him a thing - cook a really nice meal for him or something along those lines. The best gifts I've gotten weren't products they were memories.

What are his hobbies or personal interests? There are multitude of things that can be suggested but ideally one that best matches or complements his hobbies and interests are ideal.

i like it when my GF gets down on her hands and knees and crawls to me...says that she's been bad and needs to be punished...and then things escalate from there...50 Shads of Grey style..but so much more.

I'm also really touched when my GF writes me letters and notes for me to find in various places...maybe its old fashioned...but those notes really touched me.

but also...the hot slave sex...

Gaming console with WFH, lockdown and all? And you'll get into it too, trust me.

Some good head and sex.

A few LEGO Duplo sets plus a case of Nesquik outta do the trick

Yes