DALLAS -- While many online video games are free to download, some can become more and more expensive as you get further into the game.

The massively multiplayer online role-playing game Maple Story allows users to buy everything from clothes and flowers to plastic surgery for their characters with real money.

Tech expert Cali Lewis said parents should take the time to watch their children play online games.

"It's not a bad thing if you can teach your kid to control the usage," she said.

Game makers encourage players to use good judgment and said they can't be responsible for kids who go overboard.

According to some teens, the virtual worlds are the hottest new places to hang out with friends.

Flying helicopters, magical powers and monster battles can be found inside the massively multiplayer online role-playing game World of Warcraft.

"I spent a summer playing it, staying up until 4 a.m. every night," gamer Stephanie Stefanski said.

She said the brother of one of her friends plays "24-7," but she stopped the marathon sessions when school started.

The teens NBC 5 spoke to said they believe online games are designed to suck them in so they spend more money.

"I could see how you could really spend a lot of money," gamer Andrew Willis said.

Players can download a trial version of World of Warcraft for a limited time, but must purchase the game at a store and pay a monthly fee to play it.

"It's all social status," Stefanski said. "You want to have your character looking as cool as possible with the rarest items."

NBC 5 found a Web site that had World of Warcraft character accessories for sale and sold high-level characters for more than $5,000.

However, the game's developer and publisher, Blizzard Entertainment, prohibits the sale of in-game currency, goods, services and characters. The company bans players from the game who are caught buying characters and also penalizes players who purchase in-game items with real money.

Willis said he tries not to play excessively.

"I'm going to keep playing it and try not to get my life sucked in," Willis said.

Stefanski agreed.

"It's a fun game, but you can't let it get a hold of you, because it's just a game," she said.