About sales: the game is still available in box form from game stores and online (such as Amazon). The digital sale stop was not meant to completely stop incoming player population, just to slow it down.
Furthermore on this topic, ArenaNet has been trying to keep the number of servers low so they don't end up with a lot of empty servers when the initial hype dies down. Though, due to player and guild names being globally unique, doing server merges are much easier compared to other games.
About bans: ArenaNet is banning for exploiting because they want to send a very clear message that exploiting design errors will not be tolerated. If something seems too good to be true, it probably is and shouldn't be taken advantage of. There was an item for that that was selling for a fraction of its expected cost, so some people bought hundreds (or thousands) of that item to be used for other purposes (crafting and mystic forge). ArenaNet banned those player. People that did around 50-100 purchases just got a 3 day suspension.
To add, people that were banned are being given the option to submit a customer service ticket and have their account unbanned and converted to a 72-hour suspension instead. They must also promise to delete any items or money they gained through the exploit. This was done as it was the first exploit found in the game.
ArenaNet is doing all this to send a very clear message on how they expect their players to behave, and I'm happy they are.