Just a little mumbling here… 425 SF for $11000 +/-. I’m going to take a stab at the concrete, posts, decking, framing, railing, and hardware at $10/SF, so you’ve got $4250 in that, leaves you $6800 for labor. You the journeyman and one helper, total billing rate of $85 per hour, I’ll pencil in 56 hours to get you in and out of there, that’s $4760, now we’re at $9010, divide $9010 by .8 and you get $11262. Pretty close to your bid.
Now, I can’t see it from here–is it a hairy steep slope with buried boulders, or a flat lot with topsoil? Hand carry the lumber 500 feet up a set of landscape stairs or drive the truck up to the deck? And, I’m guessing at the materials–what did you come up with?
Anyway, that’s how I’d pencil it out.