Be careful because you're comparing apples to oranges. LinkPoint and Authorize.net are just gateways, they are connectors between your website and a merchant account, and don't do anything on their own. PayPal is a complete solution for accepting payments.
Authorize.net pricing also depends on what company sells you the account. They do not sell their services directly to end users (merchants), and merchants have a number of pricing options to choose from that they may offer you, some more or less expensive. Then you also have to consider how you're going to do the recurring payments, as there are multiple options there too.
1) Using "automated recurring payments", at a monthly cost. You don't have the option of easily performing variable amount payments, you don't have much API access to modify the subscriptions, you can't do one-time payments in addition to the monthly payments without recollecting billing information.
2) Using "customer information manager", at a monthly cost. Rather than have the gateway automatically charge your donors each period, you store their payment information at the gateway and send the request to charge them on your own schedule from your own software. This lets you change the amount of each payment very easily and change the schedule very easily.
3) There's a third option but it's not really an option that should be discussed on this kind of forum as it leads people the wrong way.
You will have (literally) dozens of different fees to compare when you look at the merchant account to go with the gateway, some of them transaction fees and some of them monthly. With PayPal the fee structure is very transparent, with a merchant account it is not, and you can end up paying much more than you expect.