Bukkit

What steps will reproduce the problem?
1.Buy a ton of items fast
2. crash's the server
3. buy a ton of items, sell them fast abuse of the system to make money

What is the expected output? What do you see instead?
I expect players to be able to buy items without spamming it, also players are abusing it by buying and selling very quickly
to abuse the market
What version of the product are you using?
Newest version

Do you have an error log of what happened?
http://pastebin.com/WSxcN7Mg

Please provide any additional information below.

You can prevent users from abusing the system by adding taxes. For example, if the price change speed is 0.25% and you use a sign to sell/buy 20 items at once (the amount on the sign is 20), the price will change by 5%. You can stop people from profiting by buying and immediately selling using this sign with 3% buy tax and 3% sell tax. This will charge them a total of 6% extra so that they make a loss by buying and immediately selling which should give them an incentive not to do it.

I do not know about it crashing though. People on my server spam the signs to sell lots of items quickly without causing any lag at all. How many people are buying and selling at once? How many items are you trading per transaction on the sign?

@Mako_Shark: Go

They are selling 10 at a time, And usually there is not more then 1 or 2 people buying at a time. But i think there is a permissions error because the permission [dynshop.customer.buy.sign: true] crashes my server totally. Also Would there just be a possible way to add a cool down on the purchase's? And did you see the error above ^ I think thats one of the major problems. Thanks!

That permissions error is very strange. Does it crashes every time or only if somebody really spams the signs?

@SchwarzerZylinder: Go

It seems that using the signs is contributing to it but I had to disable the plugin until this was problem is resolved.

UPDATE: confirmed spamming the signs causes MAJOR lag sometimes crashes the server