Some people do do two layer (4in) tall sheet cakes just like their regular cakes.
How much do you normally charge for a 1/2 sheet cake, no fancy detail just airbrushed colors? This is my first sheet.
Uh oh....the big, "how much do I charge" question....
Most people on here would say:
-depends on where you live...
-charge no less per serving than you would for any other cake
-depends on the details, icing, etc.
Not legal myself, so can't help much...I'd say check a few bakeries in your area and see what the competition is charging and set your prices accordingly. 
By Wikipedia definition, a sheet cake is a single layer of cake: http://en.wikipedia.org/wiki/Sheet_cake
And the same on this site: http://www.wisegeek.com/what-is-a-sheet-cake.htm
For my area single layer sheets
9x13 $28.00
11x15 $40
12x18 $65
Hope this helps
I have done a 2 layer and filled it. It will feed alot more that way. It depends on your needs
Of course! A 2-layer 9x13 is twice as much cake as a single layer 9x13, so it's twice as much cake and will feed twice as many people. 
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