Okay, rams are getting a bit of a bad name here I see.
I've kept them, and yes they are territorial, and they are sensitive, but keeping them is not as hard as it seems.
The best way to keep them is to create a lot of little caves and hiding holes near the bottom of the tank, also create some natural barriers. Rams tend to stick to the lower and midlevels of the tank, only really going to the top around feeding time, so you can leave free swimming space for the other fish at the top and upper midlevel.
Here are some tanks illustrating the kind of setup I mean.
123Rams tipically don't really attack other fish, they may chase them away from their home, but wont pursue them all around the tank.
When keeping multiple rams it's best to get eighter two females, one male & one female or one male & two females. Make sure you don't have more then one male, or at least more females then males. Rams also need their space, they aren't schooling fish.
Sexing the ram is ifficult I find. The female has a red belly and the male is supposed to have pointier fins, but in the store they are usually too off color.
Male &
FemaleRams by nature tend to avoid each other, and they are often called peacefull because they can't be kept with more agressive fish. They are quite fragile and horrible fighters. When fighting it's usually by flaring and executing faint attacks. Only in an overcrowded tank they'll kill eachother. In comparation they are less agressive then angelfish, bettas and some mollies I've had.
About their prices, I don't know about america, but they are not the most expensive fish I've seen on the market in europe. They are cheaper then some plants sold here. +- €4,-
Oh and about guppies, I've never had the overpopulation problem. What I did have was the inbreeding problem, my population died out by having too many weak misformed young.
The best way to prevent population problems is to only buy one sex, or you can set up breeding tanks and try to trade excess guppies for other things at the petstore. I used to do that with guppies and tilapia. They'll probably just become feeder fish though.