The pay for themselves in 2 alignments. You can make your own adjustments to get things really dialed-in, and you can change settings for different tracks. Also, whenever you change ride height, you're changing alignment too, and should re-align. It's very satisfying to watch your camber gauge change in real-time as you make small adjustments. And you can see your toe measurements change by the 1/16 inch as you turn a tie rod end by one or two flats on the hex...and then adjust the other side to keep them exactly "boxed" within the cables from the rear end, giving you the 4-wheel alignment.
One note: although the full weight of the car is on the hub stands, the suspension is not completely settled, because it has drooped when you jack up the car to put the hub stands on. You can settle it pretty well by pushing down and rocking the car, but after a drive, your settings may be slightly different from when on the stands. Adjust accordingly.