Fee based on payment processor
Unfortunately I don't think this is possible to do without a small amount of development work.

If you did want to add this as a feature there are several approaches:

1) You could modify the contribution template file yourself (or pay a developer) to add some javascript in order to do this. You would probably also need to configure the page to have a price set field that is the "credit card fee" or something similar. There is more information about how to append a template page here:

https://wiki.civicrm.org/confluence/display/CRMDOC/Page+Templates

2) You could contact the core team here and request a new feature using the paid issue queue: https://civicrm.org/paid-issue-queue. CiviCRM has a new monthly release cycle so your feature could be built relatively quickly.

Best

Jamie