Estimates are always tricky because costs vary so much in different regions and for various other factors, but installation for a basic system should cost less than $400 for installation (not including the price of the unit, which of course also varies).
if you call the right plumber ( like cousin mike v in marietta ), $ 400 including heater & expansion tank - yes, he's licensed AND insured, too
are you looking for a good heater or one from the big box stores?
the question not yet posed, how long do you plan to stay in your home? If for awhile... please give serious consideration to a tankless water heater! initial cost is indeed higher, but the ROI can be good if you are staying for a few years (also good for resale value)
More info? http://designsbybsb.com/2011/12/hot-water/
we considered ' tankless ' at the shore but our plumber advised otherwise,,, my marietta plumbers like them for new const but retro's a no-no,,, just their $ .03,,, do they appeal to those trying to ' green up ' ? absolutely !
I just replaced mine last month. It is a 40 gallon in a basement. I got quotes ranging from $650 - $1900 inclusive. All from licensed and reputable plumbers. I wound up paying about $850. The tank is a Bradford White (not avail in big box stores).
You can go tankless and get in and out of the whole thing for about $2400 for a 4-5 bath home. You can free up that space and get a series of tax credits that add up to about $600. You can start saving roughly $35-$50 per month on your gas bill and the next thing you know, you've got the forever hot water system operating in your house for less money than the traditional, more costly to operate, tank water heater.