I may not be able to speak for many in the food industry, but I might be able to get the ball rolling in discussing attributes in the service industry.
For example, technically, I am a "Wisconsin reseller."
First off, I need a license and I must charge each client 5.5% sales tax for every product and service dispensed. During the intense gasoline pricing of 2007-08, I also had to charge a 'fuel penalty.'
My sharpening stones wear out. They cost +eight dollars per each, plus shipping. In a good month, I go through at least two of them. This does not take into account all of the tools purchased to even start my services. That is about 4,000 dollars, and it continues to mount as new products hit the market.
Then there is prep time. This involves cleaning of the knife (yes, many arrive filthy), polishing the decorative bright-work, taping the decorative portion of the knife with blue painters tape to avoid scratches, clean up, repair, etc.
Some clients want the knives picked up and delivered.
Business cards. My own shipping cost for new knives out of pocket. Legal fees. The cost of a tax accountant. The cost of test knives ("mules") that will be damaged, destroyed or sold below cost. (In another thread I mentioned the purchase of a Chinese cleaver which may or may not become a stocking item.)
As you can see, any sole proprietor runs up costs many might not consider--including health insurance--and any purchase out of pocket, no matter how slight, effects his end result bottom line. And let's be honest, any good guy is going to do pro bono work.
I charge 20 dollars per inch on high end Japanese kitchen knives. Considering the expense here, it's not a great deal.
For example, my doctor is Japanese and he owns many real-deal knives which have been handed down to him over generations. He ships them to Japan to have them sharpened (polished is the correct term) by a togi-shi.
Imagine his invoice...