Price blood dealer, or a percentage of sales

[Art_Lyss]

One galeristka told me: Interest paid only once.
But, I would add that the price of such a board-damaged relationship with the dealer. Chrevotochinka heart and memory. Belonging to the category of speculators.
I unfastened the dealer tempted percentage, if 2nd time to sell the painting to its customers. At the 3rd - a donation. Although the dealer and doing nothing. But, he brought new people, and causes more-in atmosphere of mutual respect, honesty and circumscribed.
Generally, it seems that the height of interest depends on the actions of special operations. When scale loyal to pay and 50%. Commission is now taking 10 to 30%. Thanks for inactivity dealer-5%or meadow.
Who has what was the experience?
What do gallery owners and dealers?
What do artists?