I personally am always disappointed by how much a seller of used miniatures thinks he should get. The conversations verge on the surreal sometimes.
Primed miniatures are a worse value than unpainted because the buyer can't trust the priming quality, and in many cases they are chipped and the buyer has to reprime anyway, and may strip first. So they represent additional labor and uncertainty. Also since the packaging is not available, there is some worry that a bit or part may be missing.
I would say if you think of them as being worth half what a new unopened miniature is, you won't be too far off. You could hold out for a long sale, looking for that buyer who feels your minis will save him priming and assembly time. But that is more certain in person, and even then won't apply to everybody.
(See my post on your topic about unopened miniatures for the price reasoning.)
So for a long sale, 70% online, 75% in person. For a quick sale though, 25% online / 30% in person.