What is the ruling on spending vast sums of money to purchase a grave? And is purchasing a grave even required in the first place?

Purchasing a grave is permissible, and its legality is confirmed in places where graves are scarce or where there are no endowed graves for the needy. The expenses for preparing and burying the deceased are taken from their wealth. If they have no wealth, then the expenses fall upon those responsible for their maintenance; otherwise, they are covered by the public treasury (Bayt al-Mal). Exaggeration in preparing the deceased is not appropriate; rather, economy is required. There is no obligation to increase the shroud's cost from the public treasury, just as exaggeration in grave costs is legally disliked (makrooh), similar to exaggeration in shroud costs.