This is one of the reasons many people on this forum have turned to mattress kits and Frankenbeds. Manufacturers and merchants collude to prevent the consumer from knowing exactly what they are buying or from comparison shopping because the same mattress is sold under a different name at every store that carries it. The manufacturers won't help you because they want to protect their merchant's "exclusivity." And most retailers are very cagey about exactly what's under the hood.
Occasionally you can find those cutaway samples that show you what the construction is but even if you do you'd have to find another one somewhere else to compare it. I've only come across one chain--Mattress Giant located on the east coast and midwest, that actually provided a detailed list of materials used in each of the mattresses they sell on their website. But they still play the exclusive name game.
If you have perused this forum you will know that mattresses made with PU foam don't hold up no matter how much money you spend. The general rule of thumb is to buy one with the least amount of padding. Stay away from pillowtops. You'll be sorry if you don't. Get it as firm as you can and put your own comfort layers on.
Oh. and one last word. A salesman will always tell you the mattress he sells is better than the one someone else is selling--even if it's the same mattress. That's their job.
And yeah, $1820 for a mattress is way too much--considering it's going to last three years if you're lucky, less if you're not.