I hate when a seller gives the impression something is of their design, that they've put their everything into an item or line of items and you find out that they bought the item(s) from someone or somewhere else and are reselling them.
It's not the mark up that bothers me so much as the misrepresentation. I don't care if you didn't make or design the item yourself, but when you go to great lengths to give that impression, then I wonder what else are you willing to do to make a sale.
I've come across this twice now with two different sellers. I stumbled upon the actual designer/maker's websites quite by chance. And even though I considered myself a loyal customer to those sellers who misrepresented things, guess who I'm buying the items from now -- the actual designer/maker. And while it's considerably cheaper in some cases (one item I purchased for $15, but the actual maker/designer sells for $5), it's the feeling that I was scammed by those first sellers that will keep me purchasing from the actual maker and/or designer sites.