I agree with @YourBestTrader . I'd prefer SleepQA (available to hand reg) before I'd add the n. SleepFAQ is listed for $4,700 and I'd say that's your best bet shooting for the stars.
I personally own a few sleep related domains and don't assign them any value outside of potential for development...which is impressive. Affiliate commissions on some of the most popular mattress brands range from $75 to $400 per sale and I've seen multiple sleep sites sell for over a million.