I have hunted the Snoqualmie Tree Farm for many years. As far as being "over priced" that is your opinion, I personally don't believe that to be true because it is some of the best hunting in the area, and also has some great lakes. If it is "over priced" then 500 people wouldn't buy the permits up in a little over two months. Heck up until last year they never sold out, and the prices are higher now then ever.
As far as the Snoqualmie Farm the permit is only required to drive, you can walk/bike in all you want. But the "good" areas for grouse are quite far in and unless you have a bike I wouldn't do it. I don't know where you live in King County but you can also try the White River Tree Farm which is also owned by Hancock and requires a permit for the same fee and is also sold out. White River Farm is in King and Pierce Counties and straddles SR 410 outside of Enumclaw. I have quite a few grouse in that area.
Personally though your best bet would be the Snoqualmie Farm, have limited it out many times up there.
And no you don't need to be high in elevation for grouse, the Blues tend to stick to higher elevation but have seen grouse just driving King County roads in the Black Diamond/Enumclaw area.