If I understand this correctly. Steve designed the shoe. Right?
If thats correct, it's his insight, vision and, talent that got you interested in this pair of shoes.
I'm not aware of Steve's arrangement with E.G. That's none of my business. But, if he spent his time and incorporated his experience developing the shoe, Just pay for it, as you were willing to do.
For the Lawyer's out there, this is an "intellectual property" issue. A case where it doesn't pay for a small...