I reserve the right to disagree...
The most profitable vendor that works the local events is the lady that sells fresh lemon aid! It's all she sells. Works the stand by herself , only has to buy lemons, sugar , and 32 oz foam cups. I've seen her gross $2500.00 a day and when you consider that she has no pay roll, that's good money for a vendor. And that's after the event got their share.
Putting out one high quality product that people want can reduce your overhead, cutting expenses, increase your quality control and efficiency of sells, leading to more net profit.
Hardee's finally learned that after years of loosing money trying to be a jack of all trades.