"...going to cost the taxpayers a ton of money to have them removed"
I'm sure somebody would want to give them a good home. You can start an adopt a tablet program. Group together, pay for the removal and buy a prominent piece of property downtown somewhere and set them up with huge spotlights.
As for the laws of the country, I firmly believe that if the law has merit for society as a whole, you should not have to rely on "because God said so", you should be able to argue your case based on facts and logic.
Most of the Ten Commandments are "self evident" so to speak and easily arguable in terms of respecting the rights of another, never having to refer to where YOUR conviction originated.
Others are not so easy to argue, for example coveting your neighbors wife. Is it good, no. Is it worthy of prosecution? I don't believe so. If you don't actually take any action other than to covet, then no, and even if you have a fling (Thou shalt not commit adultery) , that is an issue between two losers and one rightfully angry person, not a criminal offense in my opinion.
Some are a direct infringement our rights (Thou shalt have no other gods before me) That is pretty much the antithesis of freedom of religion
The laws of the U.S. were based on many many things from Hammurabi on up the time line. We chose some and threw out others.
There are only 10 commandants, and last time I looked, there were a few more U.S. laws than that. Thats a pretty small base for a pretty big building.
Also, the Ten Commandments are foundational to our legal structure, not the origin or destiny. You correctly point out that we have more laws than just these 10... see previous point.