I got their system 2, which includes a 10" sub, and it has more than enough for me. Deeper and cleaner bass than I had with 2 JL W9's in my last vehicle. And the highs are so clear without fatiguing your ears. I think they will do a system 2 for $3K consistently now that they've done more of them. Usually their system 2 is $4K, but they gave me a discount for letting them have my car for an extra couple of days to do some R & D on it, as it was only the 2nd model 3 they'd done. They really do what they can to help you if the price is tough for you to swallow, and it definitely was for me.
If you get their system 1, it would include an 8", but a much more powerful one than the stock system has. You would have to talk to Rick about pricing, but I would guess that their system 1 can be had in the model 3 (assuming you have Tesla's premium sound system) for about $2500. Remember, they are simply building the best system they can for that individual's tastes, car, and budget. The model 3 has good acoustics and newer audio tech in it, so can build you a system that sounds awesome (and that they're happy to attach their name to) at a lower cost than nearly any other vehicle. They get all their business from referrals, so the better system they can provide for less money benefits them. When I went down there, I told my wife that their prices were well above what I was comfortable spending and that unless it was easily the best system I'd heard that I was going to politely decline. But when I heard the same system in the model S that they were just finishing up, I had to have it, and I'm not someone who makes emotional purchases like this. I know this sounds like a commercial, but I am only this passionate because their product and service is just better than anywhere else, and I want to help people who really value great sound find it. Rick deserves all the business I can send him, and guys who want top notch audio deserve to have others that had good experiences help them find it.