What do charities expect from their website?

My team and I come from a high-calibre background having worked on web projects for some big name charities such as the British Red Cross, Cancer Research UK, WSPA, the British Skin Foundation and many others.

It was whilst working for our previous employers that we noticed how many charities were being, in our opinion, over-charged. We regularly saw prices in excess of £15k being charged for under-performing, low quality, buggy sites which didn't seem right. We even saw one client get charged around £5k for a free WordPress site(!)

We now run our own web development business and we're aiming to be better (and fairer) than that but we're interested to hear what charities really look for in a site. What influences the decision with which agency is hired? What stops charities moving away from poorly performing agencies?