I agree the fee you get goes in the income column always; the question is the degree to which the outlay is a deduction -- all the meal, half the meal, the minimum required to be purchased by the client, or only up to the amount you received.
And the other question is whether the mileage to get there is deductible or not and that is where I would recommend drawing the line. If there was no chance of making a profit, at the very least you should not turn the job into a deductible loss.
But each person should make the decision how to handle these things either in discussion with their tax professional or after doing their own reading on the irs.gov website and making their own decision based on what they read. Nobody should be taking anyone's tax advice from this forum because nobody here knows anyone else's entire tax situation. A lot of the tax code has to do with your intentions and "all facts and circumstances" and two people doing the exact same thing for different reasons will have two different outcomes on their tax returns.
If I sign up for a job in which the outlay will exceed the income, I cannot possibly have a financial profit motive. In the case of a fine dining shop with no fee or minimal fee, the obvious "reward" is the meal. Therefore, the income is the meal. Logic would say all of it is income, less mileage to get there.
However, logic is not written into the IRS rules. If you're not willing to research at IRS.gov and make a decision on your own, get a tax professional. This is not the place to figure out debatable tax issues.
There is also a category of reimbursement only shops that MSCs use as a gateway to their higher fee/value shops.