Building a pool can be expensive, but it depends on the size and features of the pool. For example, a simple above-ground pool might only cost a few hundred dollars, while an elaborate in-ground pool with all the bells and whistles could cost tens of thousands of dollars. A big factor in the cost is the labor involved in excavating and installing the pool.
The most expensive part of building a pool is the excavation. This is because the contractor has to dig a hole in the ground and put in all the infrastructure (pipes, rebar, concrete) to support the weight of the water.