Well, they don't...but, this "easy money" glitch is a nice treat for those who lost all that time having to replay 20 Chapters to progress.
Essentially, here is what happens.
When you pick up Pirate Seas you get a magic item called the "Hidden Treasure." When you place this item on the portal, it pops up and Eon announces that you can now find the "Hidden Dragon's Treasure" or something along those lines (it is 3:30 AM and I'm not concerned about perfection here).
You basically walk around till you find it (three circles light up), and then you get cash. That said, when you pull the item off the portal, you can put it back on, and repeat.
That is nice, but you'll wander all over the Ruins or a level looking for the treasure chest...if only it could just reappear in the same spot every time...
Well it can!
Once you find the Hidden Treasure, you can go talk to anyone, back out, and go find the Treasure in the exact same spot. This is good, but not great...You still loose time meandering from the character to the location of the chest.
Fear not! If you get the Hidden Treasure by Persephone you are set up for this great trick. (This will work with any character (close to T-Bone, between Cali and Flynn etc), but Persephone is the best). Once you get the Hidden Treasure to pop-up just to the left of Persephone, go talk to her...you can even cut her off by backing out of the dialogue. Stammer back to the left and voila! Hidden Treasure.
You now just repeat this as many times as necessary to get the cash you need. This is very helpful if you are in a hurry, are just a few hundred short of the next power-up, or are just taking 2nd Skylanders thru the paces and are just wanting to go down the other Upgrade Path etc.
If you need to "Level Up" in addition to collect cash, I would still suggest Quicksilver Vault. That said, if you just need $500 to get a Soul Gem, pull out the Hidden Treasure and go to town.
Amazingly, I have barely used this (despite knowing of it for a long time). The recording you see here was really the first time I'd gone in-depth with it. Since that time, I made great use of it rounding off the Skylanders for the Mass Ugrade vids...which are coming soon.
Hopefully you find this helpful, if you didn't already know, and I know it will come in handy. I know this works on Wii, but I am not 100% on other consoles...I'm sure someone can chime in on the subject.