Original 1chipMSX, complete with box and accessories

It's original, just as it came out of the box.
I may have toggled one DIP switch in order to make it display graphics on certain screens.
I can throw in a universal converter for the power plug, and cables for the video.
Does 500 euro look reasonable?

400 euro plus shipping costs can be agreeable to me.
In your case, Wolverine, you could forget about the shipping costs and I'm-a bring it to you along with a few beers.

Will ya bring beer international, too?

I suggest putting it on eBay as you’ll have a much wider audience. Make some photos of the machine hooked up to a screen so it’s obviously working and show of with Metal Gear 2 running (that will generate interest). And if possible offer to include a keyboard / VGA cable (so it is ready to use by the buyer).

Agreed, all OCM on eBay are €550 or up (and come from outside the EU so tax might be charged). Now if you would ask around €450 you would definitely stand out and draw attention. Which is what I would call a fair price for both buyer and seller.