Great suggestion! At least it's a great way to compare prices on beds you might see in various showrooms.
I bought an extra firm queen size Piero innerspring mattress (non-pillow top) at their outlet store in 2006 and later bought a used two piece La Cardeuse sommier (boxspring) on Mercado Libre for much less than it would have cost new.
The mattress is still as firm as when I bought it, but I hardly used it until I moved to the country in 2010.
Having slept on a high quality foam mattress for a month in San Francisco (exactly ten years ago) I suggest you check them out. especially if you are near a cell phone tower (who isn't in the city?).
If you buy an innerspring mattress I suggest you consider turning off your router (if you have one) at night. When I lived in the city I almost always slept on my futon, so it wasn't an issue.