Is there any difference between using credit card, debit card or Electron card?
Depends on the card processor being used. Some charge a flat rate and some a differential rate.

Many outsourced booking services take their cut from the purchaser rather than deducting it from the ticket price. For organisers working on a tight margin that provides a good way to provide for on-line sales. However to insist that tickets may only be purchased in this way will look like a rip-off to the general public.

Sorry Ms Crump, Joe Public is concerned with perceptions not with your explanation.