Paypal is a convenient way, how to send money. However, it is not for free. For example for not profit organizations inside of the USA is fee 2.2% plus fixed fee $0.30. If someone would send to organization $102.55, organization would retain $100 after paying fee $2.55. Try it in this simple calculator below.
Payment Including fees: ( amount / 0.978 + 0.30 )