Who needs toys

So, I took the kids to the park today.  After swinging for about 10 minutes and going down the slide once or twice, they declared they were bored and spent the rest of the hour and a half that we were there playing with rocks.  They do this every time we go to the playground, whether it is by ourselves or for playgroup.  The playground holds their attention for like 10 minutes, and then they spend 2 hours either piling up the mulch to make volcanoes, or gathering sticks to build a fire, or playing with rocks.  

They do this at home too.  They play longer and nicer with paper airplanes than they do with any of the toys we have at home.  Not than I am complaining.  Rocks, sticks, and paper certainly are cheaper than all these toys we have.  It makes me want to just sell all their toys on Craigslist and get rid of them all.  Of course, I would have to do this while they weren't watching, since as soon as they knew I was getting rid of their toys, they would suddenly become very attached to them.  

Maybe I could just give them some sticks and rocks to distract them while I did it...