chadbiggs - You've answered your own question. You purchase them. The price depends on the developer but if I were to guess since it is a complex game especially that it is a multiplayer game then it will cost you about $1000+ but if it is a very high designed game then that will cost more than that, you will be like a company buying a game and that price isn't like the regular prices. Unless if there is a game licensing available for that type of game category then it will cost less like $5.00-+ but depends again to the developer, here you can buy them if there are any: https://www.scirra.com/store/games
Why not just buy a game, like Xbox or PS4 games? You'll save more that way.