thanks for your thoughts and the interesting, since very hypothetical and detailed question.
I think the key concepts you are working towards here is a) opportunity cost of choosing this investment and b) return on investment.
In the context here, I would ask the interviewer for three key aspects to determine that:
- Total size of the investment: 10% profit is great, but what is the size of the investment? Is there also a benchmark for the size of the usual investments that this company makes and where does the Milan airport restaurant stand on this list? This would give us an idea as to how much sunk cost we would create
- Portion of upfront investments: In relation to the total investment, what portion of that does a) the license and b) other upfront sunk cost such as the real estate agent take?
- Amount of other available investments: are investment opportunities limited or not? This would help us to put the value of the opportunity in Milan into context.
Answering these three we would get closer to make a quantified comment on the opportunity cost of foregoing this investment and on how long we would need to have the license to be valid for
Do you have any info on the above?