I'm seeing something different on (my local) Braintree site [1][2]:
> All processing fees, except the per transaction fee, are returned for full refunds. For partial refunds, all processing fees are returned at a prorated amount, but the transaction fee is not returned.
[1] https://www.braintreepayments.com/sg/braintree-pricing
[2] Looks like the US one has the same policy as Stripe: https://www.braintreepayments.com/braintree-pricing?locale=u...