All I can say that while people will get bothered by a price change, as long as you didn't promise the person the low price and had them drive to you, then there is no foul play.
I wanted to sell a Radion and RMS mount for more money than I got it for because a) I got a good deal, and b) I didn't have a use for it anymore, but I knew people would ***** and call me a flipper. But really, it's the owner's right to sell it at their desired price despite of what they got it for, unless they got it for free with the promise not to sell it for profit or something.
So my question is....did you promise the buyer the item at a lower price and then change your mind? That's distasteful, but still not inherently wrong.
And did you make them drive all the way to your place and then change the price? That I find pretty reprehensible.