1. Is taking a lower salary just the cost of working at a startup as compared with a FAANG?
2. Is it stupid to decrease your salary by that much when changing jobs, or is this something that everyone does in exchange for working at a smaller company?
3. If I know they can't pay me as much as I currently make, but I still want to work at a startup, what should I tell them when they ask me what salary I'm expecting? My current salary? Something lower?
Yes. In theory you should get some equity that rectifies the lower salary when the startup exits, but that's very risky because many never do.
Maybe you're already aware of this but I'll point it out just in case - many people find building the sort of things startups need in the early stages boring as hell. Most of the work is CRUD stuff and deployment pipelines. There's very little time for the fun bits. You should validate your assumption that a startup would be more interesting to you before making the leap.
2. Not at all. With FAANG you're optimizing for compensation and resume prestige. With startups you're optimizing for learning opportunities, professional growth, faster pace, etc. You'll find that at different stages of your career you will start to optimize for different things.
3. Don't give a number. Indicate why you're interested in the company and that you're targeting the market rate for a company their size. Ask them for the role's comp range. Have a lower bound in your mind, but be realistic - a startup simply cannot match the compensation of companies that bring in billions in revenues.
Yes.
2. Is it stupid to decrease your salary by that much when changing jobs, or is this something that everyone does in exchange for working at a smaller company?
No, it only happens when you downgrade from FAANG (or from a small set of unicorns with similar compensation ranges). Whether it is "stupid" or not is up to you.
3. If I know they can't pay me as much as I currently make, but I still want to work at a startup, what should I tell them when they ask me what salary I'm expecting? My current salary? Something lower?
See the advice in sibling comments (e.g. romahn's). Whatever you do you'll have to be prepared eat a 30-50 percent salary decrease. What's up to you is how you spin this fact in your negotiations.
Getting back to what you said at the top:
The money is great, but the job is boring.
By all indications, this precisely what FAANG pays you for - to stick around and put up with whatever they throw at you.
It was to test your appetite for this level of boredom that they made you do all those LC problems, after all.
It seems unfair to him, but the expectations of a superstar are a lot higher.
You can negotiate a superstar ex-FAANG salary, but you have to justify why you're costing them 6 months of runway. If you're at a FAANG, you can increase click rates on ads by 0.1% a quarter and that would already justify your salary.
At a FAANG, their question is how low they can pay you and where you compare to the rest of the applicant pool. For a startup, they have maybe 5 applicants. They want someone who can keep them alive long enough to the next round of funding, up until acquisition. Sometimes that means some solid first team players. Sometimes it's a star. Sometimes it's just some interns.
IMHO it's dumb. "Get while the getting's good" is a good rule and the getting's really good at FAANGs these days. Unless the start up is doing some unique whizz bang thing that you're super interested in work is pretty much work. It's going to mostly be pretty boring stuff.
Start slacking off at work a bit and start working on a side project that interests you to scratch your itch. Do that until you're set for life and then do whatever you want.