I want to send out a very clear warning. Do NOT use the shops as storage. I have seen a massive amount of goods in the shops with a VERY high price, so only put there for storage. This has two bad effects:

• There is a higher chance that the store becomes broken. All of the plugins are under permanent development, mostly in Alpha or Beta stage and likely to have bugs. If you overload it, the chance is even higher that something breaks.
• If the shop plugin ever breaks – and so far EVERY SINGLE plugin has been broken for some time or even abandoned permanently since this server started, ALL that stuff is gone. And then I do not want to hear anybody complaining about their stuff missing. I cannot restore it.

I am in talks with the plugin author to put some sort of limit on how many different items you can sell. I strongly recommend you to take those things out of there ASAP. The next update (1.8) is around the corner and no one knows if the shops system survives that upgrade.