Little background, I'm flipping used Nintendo 3DS XLes after they have been modified with custom firmware (nothing illegal, the end buyer is responsible for sourcing games). Been doing this for 5 years and with different methods (as they are updated/changed). My bundles come with a brand new microsd/sd card and usually a charger and are ready to go!

I have my adverts posted locally on Kijii/Craigslist. My buyer contacts me and asks the standard questions "How long have you had the system? Any broken buttons/controls?" I reply that it's in good condition and everything works. My buyer continues asking why I'm selling the system. Here I tell my usual situation - was a gift for my niece and my cousin didn't want her to have a gaming system as a birthday present and I was just "recouping my costs". Guy gets cold feet and says "You are sketchy as hell!" citing that I have other games and another 2DS up for sale. No, I just specialize in 3DSes, you idiot. I ended up saying "Your loss. Have a good evening."

Edit: Story has worked for me many times in the past. People seem to get upset at resellers in the Nintendo market. It pisses me off not to be able to "tell the truth", but saying that "I'm a reseller" makes people see red. Just a fact of the Nintendo/gaming community apparently. It's not like I'm making 100% ROI.