How are you managing with 13 channels?

You can't look at it in that way. Every channel have monsters in it, moving the monsters around, giving out the information to users (where characters are, and where the monsters are). By cutting the amount of channels with (as in your case) 50% would cut the amount of memory needed to run the program by 50% (well, ignore horntail and zakum for now, please). It would also cut the processor-power-need, but not by exactly 50%. True enough, you don't have to calculate where the monster's going to be in the channels recently removed, but you still need to drag in info from characters in a map and deal it out to all other players in the map. Stores drain processor-power (and memory) more than characters itself too.

tl;dr
You have a chicken-farm. The chickens eat earthworms, but they can manage to eat the amount of earthworms a day on half the area you have. If you cut the size of the farm, you'll have more control over the chickens, and have to cut less grass (if you even do so).

This is irrelevant, because MapleStory channels are each hosted on their own servers, with dedicated resources. Memory and CPU resources are plentiful, and are a non-issue. It's not like those bootleg private servers, that host all channels on one server. >_>

I've posted this explanation on Sleepywood over a year ago, when some worlds got a channel removed and a similar discussion came up:

[COLOR="Blue"]As I've said in a few posts above, decreasing the number of channels does not affect the bandwidth required for Nexon's servers, because as you've mentioned, the number of connected users remains the same. However:

The issue in question is bandwidth overhead, as in, wasted bandwidth due to server/network design. Decreasing the number of channels actually both increases and decreases this ammount of "wasted bandwidth", but whether it's increased or decreased depends on the area you look at.

As you may know, each world consists of several interconnected servers that we call channels. Because these servers are interconnected, the more servers you have, the more they will have to talk to one another, resulting in wasted resources internally. (There have been exploits where people abused delays between these servers to dupe items and the like.) Removing a channel will improve performance in this area.

On the other hand, channels are useful for breaking up the world's (example: Scania's) load into multiple sections, where players on each channel, to an extent, would only be affected by load caused by other players on the same channel. This is why channel 1 tends to lag more as a result of FM1 than any other channel. Reducing the number of channels, however, forces more people to play on one map than before. Depending on how the game's network engine was optimized, the increase in the number of players with whom you have to exchange data (like your position, attack animation frame numbers, skill commands, etc) rises sharply. This results in worse performance and more lag for each player.

As I've said before, the issue is balancing these two areas to see what needs more improvement. Nexon probably came to the conclusion that the bottleneck in performance was their servers being unable to handle 20 channels efficiently. This move on Nexon's part will most likely place a bigger strain on our own network connections. This shouldn't be a problem, however, because the MapleStory client's network usage ranges from ~2KB/s to ~12KB/s, while a typical high speed connection will give you the ability to handle traffic at least 10 times that. The problem has always been servers being unable to keep up with the load caused by masses of players. So, I think Nexon might actually be on the right path here.

This is all pure speculation, of course, and "educated guessing" based on the (very) little experience I have in this field. I hope this all made at least some sense. D:[/COLOR]

As you can see, these two sides have to be balanced to achieve best performance. This is why Nexon is calling it an experiment.