If you want unrestricted access to all the heroes, isn't it something like a $20 one time payment?

Also, this is basically a stand-alone port of Defense of the Ancients, which was originally a multiplayer map for Warcraft III that got a huge following in its own right and has a large number of variations, the most popular I believe being DotA Allstars. In addition to LoL, Heroes of Newearth is also going to be a stand-alone port of DotA, but I think HoN is going to be much closer to DotA Allstars than LoL is.

I was actually invited to the HoN beta (don't ask me how though--I don't remember), but the terrible community repulsed me. DotA has a reputation for having a playerbase full of assholes and jerks, far moreso than you'd expect even for an Internet multiplayer game. It makes it very hard to climb the extremely steep learning curve.

The challenge isn't so much from just operating your character but more from the metagame. You only have 3 skills plus an auto-attack, but you have to select which skills or passive abilities you're going to invest in while leveling (it's impossible to have them all). With dozens of heroes, you have to learn which heroes counter what, which heroes synergize well with whom, and what your hero's role should be given your team's composition. In addition, there is an extraordinarily complicated gearing system with a ton of basic gear, "recipes" which give you better gear by combining the basic items, expensive super items, etc. And on top of all this, you have to learn about positioning, memorizing the spots on the map that allow you (or your opponent) ambush an enemy by surprise, how to use randomly spawning power-ups called runes effectively, etc.

Despite its colorful, cartoony appearance, this isn't a game for a casual player. You're not going to be able to play it unless you invest some time into learning all the ins and outs. Unfortunately for you, this means reading up on tutorials, watching a ton of replays, and dealing with hecklers while you learn at a glacier pace how to use, spec, and gear each of the characters.