Spikedo, the $60 fee at Afternic is not a flat fee. But I agree that Afternic does especially well for higher priced sales. This is what (I think) I know:
Both Afternic and Sedo have a 10% sales fee. Afternic has a minimum fee of $60, also when the domain is parked at Afternic. Sedo has no minimum fee for domains that are parked at Sedo, and a minimum fee of $50 (or Euros) for domains that are NOT parked there.
But here is what I like about Afternic:
They will return 25% of any sales commission fee if the buyer was referred to Afternic by you. Since my domains are all parked at Afternic, I automatically receive 25% of all commission fees for domains sold to buyers who are referred to Afternic by my parked domain.
I calculated that I have been receiving this 25% reduction on commission for roughly 2 out of 3 domains that I sold in the last two years. Because of this I've been paying an average of only 8,33% commission on my sales through Afternic.
To give you a sample of what this has meant for me, while comparing Afternic to Sedo:
Example 1: Selling price $400
-> Afternic commission: normally $60, but only $50 on average ($45 for 2 out of 3 domains)
-> Sedo commission: $40 (if domain is parked at Sedo)
Example 2: Selling price $2000
-> Afternic commission: normally $200, but only $166 on average
-> Sedo commission: $200
N.B. This is apart from the 25% referral income on commissions that I have received from buyers that I referred to Afternic through my parked domains, and who end up buying someone else´s domain.
As you can see it's not easy to compare the two, since the net effect depends in large part on the average sales price. But I hope this will at least give you an idea. And if you ´plan´ on selling most of your domains at prices at or over $500 - I would definitely go for Afternic.