Land price is calculated approximately by 600*[1.1^(total land bought)]. This approximation gets increasingly inaccurate, but with about a 50% error for 100 land when a gap of 5 fills it isn't half-bad.
We also know that if the amount of land owned < 10, then the land price = 0.
Maximum Land Possibly Owned: An evidenced player submission for 335 land has been the highest amount achieved so far. The same player believes the maximum possible amount to be 335-341, depending on the land discounts. This does not take into account the free land given from [[reincorporation]] tokens.
The maximum possible displayable number for 64 Bit systems (long) is −9.223.372.036.854.775.807, so it stands to reason that the maximum theoretical land price is about 92 sextillion if issues are to be avoided.