The last two panels are idiotic and unfunny. It seems obvious that prices would differ from area to area, especially given that each area enjoys different features. Naturally it will cost more to decay in a plot on Whispering Heights--they took the trouble to install a storm sewer over there! Her stupid question is intended only as a setup to the unfunny punchline. In this case, it's not funny because it's true. As with regular real estate, the location of cemetary plots will be a big factor in determining price. There is really no reason to think it would be otherwise. Yet Gordy McDeath seems to have blown the minds of our fair heroes with this little tidbit.
I will say that I agree with Howard--whoever is drawing the cemetary backgrounds is pretty darned good, yesterday's first panel notwithstanding.