The prices are sometimes all over the place. A pair of  white topped Zen Monoblocks was listed on U[seles]S Audio Mart for $2,800. It included a slew of decent tubes which clouds the base price of the units. The monoblocks, correct me if I err, cost around $600 in 2008. They have non-UFO transformers and 18 year old capacitors, near the end of their useful life. I’m not sure the cost to add UFO transformers and new caps to these but it isn’t cheap.  So there are folks who are trying to move the prior versions of gear for more than the original cost.

Model dependent it seems. SE84UFO's and 2.1's seems to be easiest to get close to or at retail if they are recent builds. Ebay ?? factor in anything goes for those 2 entry models.

Older builds seem to be a chess match in buying and selling. Looks like a small fan base for white toppers if priced accordingly.

There's been 4-5 Rachael's sitting un sold on US audiomart for a while priced on the hotter side ???? but hard to put a price on instant gratification. If I didn't own 2 already I probably would have bought one.I find it surprising they are still available based on how many are waiting for one on the list.

Upper models seem to be harder to price and comes down to a seller finding a buyer I guess??

One thing for sure I'd rather be selling a second hand Decware piece than a new model McIntosh , Audio Research,well any super high end brand I just paid full retail for. PrimaLuna used market always seems to be flooded. There's exceptions I'm sure like Pass,Hagel that seem to hold strong resale value.