Ask HN: Help a novel tech entrepreneur trying to get the first sales

Hi guys, I have been developing a digital signage projects aimed at restaurants and bars. It's all done by me. It is basic in the way that is a 32" screen that show at each time of the day the most desired products to sell. Each product is showed with a professional studio photography gastronomically optimized . Prices can be changed at any time and the whole thing is automated and unattended.

When I contact prospects I try communicate the potential to make more money from the same clients, but of course I can't tell specific numbers or ROI and this is frustrating me. I am designing now the sales process and would appreciate help from experienced fellows.

How would you approach this challenge?