Is worldpay expensive compared to other merchant accounts? what is cheaper worldpay or authorize.net?

I am thinking of using worldpay.

We use Worldpay and we are very happy with them.
They offer an excellent service.
They are well known in the UK.

It looks like authorize.net will be cheaper (depending on the reseller you use).

Here is WorldPay's US rates:

Setup Fee (non refundable) US$399
Monthly Fee - includes 3 free currencies US$50
Additional charge per currency US$75
Service charges per transaction
US$ to US$ and CAN$ to CAN$ 3.25%
Multi-currency Transactions 5.25%
Transaction Fee US$0.40
Fraud-detection service (WorldAlert) US$0.10, CA$0.15