I thought exclusive, in that regard, meant that you only sell at that store, as in, being an exclusive vendor to that store.

It seems kind of silly to sell the same item at multiple stores. Kind of competing with yourself in that regard, if the commission rates are different from one to the next. 

I know other stores do require exclusive vendoring in order to get the higher commission rates. I think squid is one, (not 100% sure though). 

Daz, Rendo or RDNA don't require or even ask about exclusive vendoring. Only exclusive items.  You get higher percentages by having higer sales numbers. You get a smaller percentage boost for exclusive items. It's also quite possible a brokerage may turn down a non exclusive item, especially if you are trying to place the same item at Rendo and DAZ. Lot of vendors choose personally to sell at only one store, because you get higer perventage when you sell more and because content making is sufficiently time consuming that in most cases you spread yourself too thin trying to have product at several places.

Also, having a back catalog plays a significant role, every time you release a new, likeable item, people look at your other stuff too, and good 20% sales will come from the back catalog. If your back catalog is not huge, that effect is lost very fast. Releasing at one, or at most two brokerages definitely has benefits.

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Renderosity Store  Personal nick: Conniekat8
Hi, my name is "No, Bad Kitteh, NOO", what's yours?