Genesis once bubbled...
Its not that simple, and you know it CBF.
But heh, presenting it that way makes the outrageous seem reasonable.
There are two knids of costs in running a business - variable and fixed. Fixed costs exist irrespective of how much product you move or even if you're open. Things like rent on the building are fixed costs and, to a large extent, so are utility costs (although there IS a variable component in there as energy use does change with traffic levels, particularly in a dive shop where a compressor has to run.)
Variable costs can be broken down into two categories - direct and indirect. A direct variable cost is, for example, the cost of the mask that you have displayed for sale. An indirect variable cost is the lost sales opportunity by displaying that mask - it consumes space that you could use to display something ELSE.
Labor has both a fixed and variable component. Obviously, the quality of labor you need to employ to fill a tank is not the same as the quality of labor you need to have to run a charter boat.
The problem with blanket statements like CBF made is that they are totally irrelavent out of the context of the entirety of the operation, and no two operations are identical in their cost structures.
A dive shop located on a beach, for example, might have a rent that is three or even five-hundred percent higher than one in an industrial location. Yet the first one will have more "curb appeal", and thus more foot traffic. Does this mean that you "owe" the beach shop owner a higher mark-up on your purchases because he decided to locate there?
Nope.
This entire market format is broken. It is broken because the shops and manufacturers have conspired together to keep it that way, with each "pushing back" on the other to decry and try to prevent change. The agencies are, to some extent, involved in this too. SSI, for example does not permit its instructors to teach privately (without a shop affiliation.)
IF that collusion were to go away, or IF a shop was ballsey enough to find a way to break the mold, you could have a set of structures that was VERY different.
For example, you could have a shop that sold ONLY gear. As such the insurance requirements might go away, being nothing more than common retail business insurance (e.g. don't slip on the floor of the building!)
You could also have a shop that sold service (overhauls, etc) and fills. They might need the "traditional" insurance, or perhaps not - perhaps, instead, they would operate on a waiver system - you want air, sign here. You want a reg fixed, sign here. Etc.
You could, finally, have completely independant instructors. Again, they might need their own insurance, but that's ok - its a part of doing business. Of course they might have their waivers too (they certainly do now!)
Would I need a "57% markup" if I was a gear seller? Maybe. But maybe not. I might be the "Best Buy" of Scuba dealers, and sell a lot of gear out of the box for very little overhead.
Would I need it to sell air or repairs? Maybe. Maybe even more!
Ditto for instruction...
But without the jackbooted ENFORCED bundling, business folks would decide which fixed and variable costs they wanted, and how to best tailor their business to make the profit - and value - proposition work.
To cry that you "need" some particular margin when you signed up for a bundled offering where you have costs shoved at you without your free election to be in that part of the business sounds like sour grapes to me - and the mark of a poor businessperson who is incapable of doing their own cost assessment.
This is Business 101 folks.
I entered and left lines of business from time to time when I ran my company. THE largest evaluation item when considering the entry into a new line of product or service offering was how it impacted my cost structure.