I think that's really the rub on the issue. I've bought cases before, mostly to get 4-6 of the same parts, because I realized it would be much more economical to buy a case and part out what I don't need versus trying to gun for multiples of X and Y and Z parts loose plus all the shipping to get them.
As for whether it's a good idea to be an official dealer to get cases, yeah I don't know. Depends on the set, your tolerance for parting things out and the tedium that goes with it, and the kind of deal you get. To be a dealer, you often need a storefront or a website with a cart with a regular newsletter/catalog in print to qualify. You also sometimes need to hit certain order amounts for certain discounts on the items and shipping.
Either way you have to deal with people and that's just not fun sometimes. There are some great people out there. Some truly outstanding people in the hobby. Then there are some twice used scrotum cheeses that you hope will choke themselves with their overlong nipple hairs because they were distracted by their aching man-gina.
I don't feel either way for those that flip things, I mean we all have to make choices in how we can afford to stay in this hobby. If another guy flips to make enough coin to fund the things he likes on his shelf, as long as it doesn't impact me, good for him. Sure some make a little gravy. But they also have to deal with the tedium of Ebay or trading or running lists. Emailing, packing stuff, getting money, dealing with problems with that, trying to move the parts you know that no one wants, hoping the brand doesn't release a variant and killing off the demand for your stuff, etc, etc. Sure you can make a little extra cash and fund your own collection, but everything comes at some kind of cost. Might not be cash, might be time and trouble, might be something else, but it's always something in the end.
That being said, if you want to flip something and you aren't a dealer, you gotta make good choices. Is flipping an Elder a good idea? Maybe. But if you buy high and you sell high, doesn't seem much reward for the time put in. Is flipping a Cleaner via parts a good idea? I don't know. Many of the parts are redundant in an earlier set that you can still find out there if you look hard enough and not too far above original MSRP.
Being a dealer, from my eyes, looks like a break even enterprise. You can move only boxed stuff. In which case you almost have no competitive advantage over your rivals. Everyone is working within the same 10 percent of give from MSRP that the distributor will allow you for new stuff otherwise they cut you off for good. ( Look at Alter Ego, they have survived, in no small part to giving the full 10 percent that the distributor will allow on publicly listed prices.) You can of course part things out, if you want to, except the load outs might not justify parting a specific set out. In which case you sell hot parts A and B and C and get stuck with X and Y and Z that no one wants. Then a new set comes out. And the same thing happens. Now you got five giant tubs of X and Y and Zs from the past year and no one wants it and it's just dead money sitting in inventory that won't move and it's the same loose crap that 10 other dealers can't move either. Go to a big show sometime where there are loose parts, look how it's set up, the crap, the X Y and Z is out front where anyone can touch it. Impulse buying. The good stuff? Behind the tables and you gotta ask for it.
You gotta ask yourself is getting a occasional good bulk deal to part out not as a dealer is worth not having to deal with all that.
Scalpers, flippers, resellers, part time dealers - whatever you want to call them - don't hate them or be angry at them or even care about them. We all pay for our toys in the end, they do too, the commodity being exchanged might be different, but we all have to answer the tab eventually.
GG