The online options mentioned in this thread will help you get this done cheaply, but make sure you fully understand the docs you’re creating and filing. Forming your company is not an area where you want to be skimping on cost :)
If you want to go with an attorney, you can get a C-corp setup for no more than $2000 + filing fees. Some attorneys offer flat fee structures for creating companies (eg Walker Corporate Law: http://walkercorporatelaw.com/), many firms won’t have this fees structure by default, but you should be able to negotiate either a flat fee or a cap on fees.
I ended up going with a major firm and negotiated a flat fee of $1500 + filing fees. You’re going to need an attorney for a lot more than just starting the company and the right attorney you’re looking to build a long term relationship with will realize this as well.
Some firms will offer to defer $10-20k or so of fees until you get financing, but remember you’re still going to have to pay this bill later. I don’t really consider this to be a good deal. Another thing I’d be cautious of is if a firm that wants to take some equity (eg 1% or so) in order to do so. Sometimes they’ll offer a reduction in fees as part of this deal (eg 10% off). Their argument will be that it will align their interest with yours, which in a way is true, but even with the 10% discount they’re still charging you $500-600/hr. I don’t think that’s much of a deal either.
Bottom line - you can get this done online for a few hundred dollars (just make sure you know what you’re doing), or you can go with a reputable firm and get it done for $2k + fees. You shouldn’t really need to pay any more than that.