I think the Skyscale is a good example of how a reward should be. You have to work for it and it makes a big difference when you finally get it.

I did the collection(s) on two accounts and I knew beforehand that it woudl take a while. The GW2Wiki has all the information you need. So I worked my way through it without any rush, making a bit of progress (almost) every day. Nothing was unreasonable hard or expensive ...

... and both times it felt great to unlock and even more to actually use the Skyscale. (Sorry, Bunny!)