I don't think that what my beaver pelts sell for is going to keep me awake at night.
I'll have to disagree with there only being a couple of bucks difference between the grades though. Here's an example of the price difference between grades for some of mine in the last auction:
134042 3XL-XXL *I PL-XP 28.00
134048 3XL-XXL SLT PL-XP 17.50
134101 XL *I DBR-BR 19.50 (Top Lot)
134109 XL SDG DBR-BR 13.00
Obviously I'd much rather catch a *I than a SLT or a SDG but like I said, it's not enough money to keep me awake at night.