I don't use them, but I read that GoDaddy has buy it now landing pages, with GoDaddy branding if that is important to you:
https://domainnamewire.com/2021/01/26/godaddy-to-introduce-buy-now-lander-for-aftermarket-domains/
If you say that BIN is the most effective method (I agree), then I think it's a problem for you that your landing pages don't use BIN. Most customers will copy and paste the domains into their browsers and visit the landing page.
Maybe the GoDaddy branding increases conversions, however 20% commission from 400,000 USD = 80,000 USD commission; 10% commission from 400,000 USD = 40,000 USD commission (in case of domains priced under 5000 USD).
The difference is 40,000 USD in commissions. If your average sales price per domain is let's say 4000 USD, then you need to sell at least +10 domains thanks to the GoDaddy branding in 6 months, because of the higher commission. Provided you sell all domains with the landing pages. Of course if you only sell let's say 50% of your domains via the landing pages and 50% via the partner networks, then the math will be different, but it would be still a 20,000 USD difference. And of course if you have a lot of sales above 5000 USD, then you pay less commission on Afternic, so the math would be different again.
I think you could try Dan.com (9% commission + 1-2% surcharge to customers in certain cases) or Alter.com (10% all-inclusive commission), you might save a lot in commissions. And Dan and Alter support installment payments as well, and their landing pages look very trustworthy. you can still use the Afternic network.
I don't say they are better than the GD/Afternic landing pages, only the testing would reveal it.
I have an idea, why not use the landing pages of Dan or Alter only for those domains which are priced below 5000 USD, and use the GoDaddy BIN or the Afternic landing pages for domains priced above 5000 USD?
I use the landing pages of Alter.com. But I haven't used the GD or Afternic landing pages yet.