The total number of squares in the grid is currently 169 squares (it’s a 13 x 13 grid). That’s a lot of expansion. Will it get bigger? Maybe in some future update, but probably not anytime soon given the current stability issues with the existing grid size.

As for how much the land costs, these are the prices at the furthest corners:
– The most upper right square (Northeast by the hills) costs $56,000.
– The most lower left square (southwest by the water) costs $69,000.
– The most lower right square (southeast) cost $137,000.

You know you’re reaching the edge when you can see land that has no rubbish for Homer or Lisa to cleanup.