Well, think about it guys. Lets say the store is about 600 miles away from your home, thats about roughly 200$ (for gaz, there and back).
Now you buy an AEG running anywhere from 300-400$, you're at 550$. Add the 15% on top of that (82$), your at 632$.
Most of us can buy a used (or a new, depending which one) AEG along with some mags for that price.