The plugin charges added fees for using their SSL on top of Stripes fees, which is not made clear when installing the plugin. Even Paypal would be less expensive than the combined 4.4%.
See https://buynowforstripe.com and scroll down page
Pricing
Using our secure servers with Stripe costs 4.4% + 45¢ per successful transaction.
For example, if you successfully charge someone $20 then after fees you’ll collect $18.67 — which Stripe will automatically deposit directly into your bank account.
The fee above already includes Stripe’s fee (2.9% + 30¢) — we just add an additional 1.5% + 15¢ for the use of our secure servers — which makes a grand total of 4.4% + 45¢ per successful transaction.