sound proofing cost in condo/garage?

Spending $10k on sound-deadening insulation and boarding up all your doors and windows will likely not be enough. I'd give you only a 10% chance of success in a condo environment.

You'd need a room within a room, like others have said, and that can easily cost you 20-30k. It requires very heavy materials, with a very robust and isolated structure that is decoupled from the floors and the walls of your condo. Otherwise those low frequencies will be transmitted through the floor and walls via vibration. Also, the room has to basically be WATER TIGHT. If it's not water tight, the sound leaks out much better.

I lived in a condo with close houses on all sides, and the very first time I set up my drums (to play very quietly) I quickly got a knock on the door because somebody's baby was trying to sleep across the street at 1pm. I wasn't even playing loud. I was playing barely above pianissimo.
Agree, there is just no way to have zero noise. You really depend on your neighbors' tolerance level.
I have neighbors only on one side and a busy road in front. I have built a room in a room in the basement, pretty well done and did not cost me a fortune (less than 2k) but of course it still leaks SOME noise. The wife says she hears it a little but she just turns up the telly. My daughter used to do her homework right above it. We can jam in there, 4 or 5 people, it's worth its weight in gold.

Never, ever mention it to your neighbors or they will start paying attention. Always deny 😁
After spending an excessive amount of time looking into this, it seems the Whisper Room is pretty much the only option for real soundproofing. I could spend $10k building something myself, only to find out I wasted my time and money because it's not good enough. Realistically, the options are to buy a whisper room, buy an e-kit, or find a rehearsal space to rent.

I'm moving to a small town where there doesn't seem to be any rehearsal space for rent, but I don't have to deal with a condo board so I only need to get the noise down to a reasonable level; I don't need full soundproofing. The thread discussing that is below. People posted some good advice and links in that thread.