Adding a few extra dollars on top of the purchase price to cover your time/fuel etc. is fine. Unnecessary mark-ups for no reason becomes scalping.
We could be talking about the scum that are Scalpers until the next blue moon so to end my post I'll direct you to a "discussion" I had with a former collector who's beginning to turn into a Scalper...
Mind the language
Scroll down to the comments & I'm sure you'll be able to figure out who I am.