25% seems about right. Total sent to me is 855 and its 221 or accelerate. Not in contact with sender. So its pay or wait longer
You need to pay 25% of the sum of the outputs when using Viabtc's paid service? That must explain why they continue offering their free service, even when the mempool status requires very high fees. I am sure they probably make a lot of money from this.
I am surprised that more major pools don't offer similar services.