Your remix is not "virtually free", it costs just as much in mining fees- The only difference is that the mining fees are paid for by users who participate in fewer rounds than you do.
The overall mining fee cost per anonymity set is less using WabiSabi than Whirlpool, having one user pay for another does not change the worse overall efficiency.
I think you misunderstand the Whirlpool model. Only new entrants pay mining fees. Remixers ride free forever both in terms of coordinator fees and mining fees. It doesn't matter if it's your first remix or your 1000th. It's virtually free *in the long run*, not on a one off basis obviously. That's just math.
If I have a UTXO and I want to raise its anonset to 1000, which is cheaper: Wasabi which will probably require me to do 20 rounds and charge me for each, or Whirlpool which will require 200 rounds but charge only for the first one?
I am aware the mining fees for remixes by new entrants to the pool.
Your example only focuses on the benefits localized to a single remixer from the round without mentioning the downsides are externalized to new users. If all 5 participants from a round decided they wanted to remix for free, then they all become "stuck" indefinitely until the pool grows bigger with new users to pay for their mining fees.
That's a valid point, but the cost is really time then, not money. And it's what allows it to beat Wasabi in terms of pricing.
