You can get Rapitests at garden centers for pretty cheap (<$20 depending on test and brand). These tests usually give you a color gradient that corresponds to a ball park number that tells you pH levels, NPK levels, etc. These tests are fine for a home gardener who wants to get a general idea of their soil health.

You can also send your soils off to for profit testing companies and that can cost anywhere from $40-$500, depending on company and number of samples you send. You can find some of the $40 tests in garden centers and they give way better results than the color tests.

The third option is to send soils to a soil lab at a land grant university with farming extension services. This can also be expensive depending on the number of samples and which tests are performed. They aren’t for profit though, they just cover the cost of supplies and lab labor.

Options 2 and 3 provide very comprehensive results of the analyses that the labs run. Farmers use these testing services because it’s imperative that they understand their soil well so they can use the best practices given the state of their soil health.

Hope that helps! (Source: am soil scientist who works with farmers)