It is a matter of perspective. If you don't need it, it's not worth anything to you. If you need it, 10k is a decent price. Anywhere 7.5 - 10k is within reason, again, for those who need it.
Even if it's only 10%, 10% on end game has a huge impact, saving you money and time. Protection is a matter of convenience because at a certain point you can hunt big mobs in it easy... I need this set badly and luckily I completed the program and I wouldn't sell mine even for 15k. It's a really good option especially when you have HP, evade, healing, life steal....
I can perfectly understand people not really needing 10% skill bonus that much so they can choose musca instead. If you don't see its worth at 10k, you don't need it. Just like with the current weapons prices, if you think they're too expensive, you don't need one. It's of no use to you. But guess what, there are liek 30 ppl looking for high end weapon and they still can't convince the current owners to let them go for these prices.