This is precisely the reason for my cleaning philosophy.

1. I generally don't clean my own chips. I haven't made up my mind yet, and I can always clean them later. I can never put back the grunge like I found it.

2. I NEVER clean chips for sale. I suspect in many cases, particulary in scans for eBay, a cleaned chip will sell better. But as a collector first, I prefer to think of what's best for the other collector. Because some prefer not to clean their chips, I let them make their own choice. Like I said, the new owner can always clean a dirty chip, they can't restore the clean one.