Ya, if you use a third party to donate through they will of course keep some % back for their marketing and costs.
I know that having worked for a charity myself, there is a community perception that those who work in welfare should work for nothing. Charities have had to employ professional managers to ensure their very survival and most of these organisations are professionally run. Even co-ordinating volunteers takes a great deal of time and associated training costs. Professional fundraisers and Managers will not work for nothing and I don't think they should. Like any business, charities have administrative costs to meet, fuel, insurance, staff wages. It would be great to think that every dollar donated goes DIRECT to the recipient but there is still a STRUCTURE between donor and recipient that has to be funded. Without this structure the recipients would get nothing.
My husband donates to a charity that employs volunteer doctors to work in third world countries. He is kept updated thru' regular newsletters and there is a website that he can also access to keep updated. Both these info mediums take resources to maintain. Currency fluctuations would also play a large part in how much money gets to the 'grass roots'.