Don't buy land online without physically going to look at it on your own, without the seller escorting you around. The seller does not want you checking with local real estate agents to find out the actual going price for lots in the area. As others have said, that business model depends on "churn" -- people buy, make a few payments, figure out they got screwed, and walk away from the deal and give it back to the seller, who repeats the process over and over.
Get on Google Earth and Zillow sometime and look at satellite views of the area -- you'll probably see vast networks of "tracts" out there with few to no occupants. Zillow will show you the number of days on market for each listing, and some of them have been for sale for years. These land schemes have been going on for generations. If most of the lots are still vacant 50 years later, there's probably a good reason, most likely access to roads and utilities, plus minimum lot size to build because of septic requirements which is often much larger than the parcels these guys are promoting.
Edit: Kingman AZ (Mohave county) gets cold in the winter. My grandparents bought several lots in that area the early 1960s thinking Arizona = warm. They finally went to see their lot years later and were very disappointed to see that it was on a steep hillside, covered in snow. This was sold to them as "commercial property" and "apartment zoned". For all I know, you're looking at one of the lots they abandoned 50 years ago after realizing they got screwed.
Edit 2: Get on the county website and look at the date on the tract map for the area of interest. That will tell you almost all you need to know about the actual value of the land. Old and unoccupied = essentially worthless.