I did a bunch of research last night. I can't see paying $200 a night or even $100 a night just to SLEEP for God's sake!
The
conference centre (sorry, I'm Canadian) is basically at the corner of Alaskan Way and Wall Street.
Any of the downtown hotels will be expensive - that's the way it is in a large city. The cheapest downtown hotel - and it's within walking distance (provided your laptop case doesn't weigh 30 lbs. like mine does) is
the Moore Hotel. $62 single, $69 - $79 double (one bed/two) or - if you can handle having the bath and facilities down the hall - $45 or $55. Cable TV - but no Internet

. The theatre is on the National Register for Historic Places - I saw an Indigo Girls concert there in ~ 1989 - and is cool. The hotel - according to the site - looks clean but it might have theadbare carpets - I haven't stayed there. It would be an experience as it was built in 1907 - lots of marble - much of the finishing is from that time.
I also looked at
Google Maps Local Search (click on the Local Search link) using the keyword motel and found several places within reasonable cab or driving distance (or maybe walking). Anything that is close to Seattle Center (the Space Needle) is
fairly close to the conference centre. And Hwy. 99 north of Denny Way (Aurora Ave N.) is a mixed commercial strip with several places on it or not too far from it. In fact I'd guess that if you don't mind budget accommodations you could find something around the $50 - $70 range just by driving up Aurora - and it won't be on the Web.
Me? I'm staying at a campground near Lake Sammamish for $20 a night - or I'm sleeping in my car. I billed a thousand bucks in my computer repair business last month and so far about $400 this month - the business just fell off of the table. A thousand is barely enough to pay my rent and phone bill - it doesn't pay the electric or heat and it doesn't feed me. It should get better - but it may not be for a couple of months - so I have to economize if I want to be at Gnomedex.