With regards to the original topic I would just like to summarize what alot of people are saying and put it in my own words:
Perform: This is any service which entails that the person is entertaining people, as opposed to providing them with a tangible or consumable good. For example:
Perform (Instrument): This "entertainer" could then use their skill with an instrument and go perform for money by entertaining people.
Craft: This is any service which entails that the person creates something tangible which they can either use or consume. For example:
Craft (Musical Instruments): This "craftsman" could then use their skill to create instruments which can be used by the entertainer. It is possible for the craftsman to then go and sell his instruments, but he has to create each instrument individually and then go sell them to each musician (not very lucrative on a one to one basis).
Profession: This is any service which entails that the person mitigates between people with "Perform" or "Craft" and people who buy or use the products. It often entails an understanding of a multitude of topics. Here are two examples:
Profession (Music Manager): This "professional" would use their skills to: locate talented musicians, set-up performances for multiple musicians, and understand what kinds of music are popular within the culture or area. Note that this professional doesn't need any knowledge of how to play an instrument, or perform in any way
Profession (Instrument Store Manager): This "professional" would use their skills to recognize top quality instruments, be knowledgeable with locating craftsmen, and being able to sell to customers and barter with them. Note that this professional doesn't need any knowledge of how to craft a musical instrument, simple the business of buying and selling.
The other thing to use in determining if a skil is a craft or profession is the pharse in the PHB "To draw a modern analogy if an occupation is a service industry, it's probably a Profession skill. If it's in the manufacturing sector, it's probabl a Craft skill"
Cooking a meal is a service industry whereas mass producing meals (like trail rations) could be perceived as a profession.
Not realy, if you mass produce meals and then eat all the food your not making a profession, its still crafting.
However, if you had Profession (restaurant owner) or Profession (farmer) this would be a profession, as you need minor knowledge of a bunch of different things.
Basically I'm saying "Making food" is not a service industry, but "Selling food" is a service industry, thus is goes under profession (note you can still sell food without a profession that involves skills with selling the food, in the same way without any training in Perception can still make a Perception check)