Can't seems to find anything specific about Wasabi uses ZFS on Google. And Wasabi doesn't change you on egress. So I guess they are similar in terms of pricing.
Although B2 seems to be way more popular on HN. I rarely see Wasabi here.
"The developers at Klara Inc. have been outstanding in helping Wasabi resolve ZFS issues and improve performance. Their understanding of ZFS internals is unmatched anywhere in the industry" - Jeff Flowers, CTO, Wasabi Technologies
You could also search the OpenZFS repository for commits with the word Wasabi in them.
Wasabi only allows as much egress as the amount of data you're storing and I don't think you can even pay for more: https://wasabi.com/pricing/faq#free-egress-policy.
There's a number of CDNS that participate in zero egress.
(Unless something’s changed since the last time I checked)
EDIT: OP is correct for CDN but if you use R2 even as a transparent copy from another S3 like provider it is allowed [1]