Here it is, the final sticker of the campaign:
I think it’s perfect and have already placed my order for three of them! If you’re like me and love to show off your pride in our candidate -- and want to prove that you were part of the team that’s about to make history -- chip in $150 right now and we’ll send you one of them, on us."
I think they need to check the definition of 'on us'. On us does not usually include a price tag.