depends on the Artist... and on the style of the set. most sets are made in 512 so it doesn't matter what resolution you use it for.
tribal is kinda cheap but with robot and humanish sets and stuff like that you can get very expensive when its a known artist.
for a normal set like nothing that special you can say: 15-40k but as I said depends on artist and style
bagurz: It doesn't depend on the color.
but maybe you find something less expensive but reqesting one is more than searching one for sale also try to haggle
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