I think the best cot for the money is is the Camptime Roll-a-Cot. I would avoid the narrowest model as it doesn't fit a standard mattress very well---the mattress needs to fit between the rails, not on top of the rails, so you lose a couple of inches on each side of the cot for the rails.
The best high end cot is the Helinox Cot One Convertible, if you're willing to spend the money. You can use it at a height of either 6" or 15".
I have both of these cots and I usually use the Helinox because it's lighter, rolls up into a smaller bundle, and it's easier to assemble. But honestly the Roll-a-Cot is a great, sturdy product at an affordable price.
In the last two years Chinese companies have come out with several Helinox knockoffs at far lower prices. I was just noticing one by "Welodorir" on Amazon the other day, which also has a choice of two heights. (Are we no longer allowed to include Amazon links? Doesn't seem to be working)
I think this Welodorir cot looks pretty interesting. The quality usually comes down to whether the connection points (how the legs are connected to the hub) are going to hold up with your weight and tossing and turning. That depends on the quality of the plastic and the design of the hub. Helinox is particularly good at designing solid connector hubs for its chairs and cots. Helinox uses DAC aluminum and the Welodorir uses 7075 aluminum. Supposedly the Welodorir supports 350 lbs. Looks like a good contender for a cheap knockoff of Helinox. I would love to try it myself.
