This is a tricky situation, and no-one wants to get involved so this is my opinion.
Item prices are judged by their rarity. This means that if they are easily accessible e.g. Kepkhets Refuge, it doesn't matter how good they are, they still go down in price.
Collectors items are usually very easy to get hold of for a small fee or free if u already have the items that collector needs. Collector items for some people can serve as cheap "greens" and why not? They are cheaper than greens and u can mod them to whatever you want!
But collectors items cannot be salvaged. So if you put a nice 20/20 string and +30 grip on a collectors bow, you will be disappointed when you get a nicer gold bow and want to use one of these items.
Shields, wands and off-hands e.g. items you can't upgrade, will go for a quite a bit more money as people prefer to buy them to the more expensive greens. But swords, bows etc tend not to sell as collector items. Maybe this is because of the mass market of cheap gold 15 >50 weapons, i don't know.
The last thing i will say about collector items is that the general appeal makes people not trade/buy them. Not many people who say "i am wielding" will want to show a collectors 20/20 +30 bow in trade when asked about it... but you can guarantee they will show off their Drago's Flatbow. The skins are sometimes inferior to the green skins so people will gladly pay more for greens.
As for your shield. You can go and sell that shield for less than the aegis, and advertise it as having the same stats. But not many people want a "Exalted Aegis Substitute", they want the real deal. The skin matters more than anything else on most weapons when it comes to selling them, just look at the Exalted Aegis. People KNOW you have one without even asking, and people love the attention from it.
This may seem harsh, but usually thats the way it goes. Hope this helps

I'm open to other opinions and i know you are too, so wait for some more replies and see what happens.