Flurly doesn't add extra charges, it does basically the same charging scheme as gumroad but cheaper.
So if you sell a $10 item:
1%, or 10c goes to Flurly
2.9% + 30c or 59c goes to Stripe
$10 - 10c - 59c = $9.31 goes to the seller
There is no additional charge to the customer above $10.
Still cool, though obviously depends on volume. I use sendowl which is as cheap as $9 a month + Stripe fees (2.9% + 30 cents).
I used to use gumroad, but had issues. I think they've gotten a bit complacent (see https://medium.com/@atrigol/gumroad-review-things-they-need-...) so prob room in the space. Good luck!
For $10 on gumroad (see https://help.gumroad.com/article/66-gumroads-fees):
Free account: 8.5% + $0.30 (USD) per sale gives $8.85 to seller
For $10/month: 3.5% + $0.30 (USD) per sale gives $9.35 to seller
And there's other options like direct paypal connection, where gumroad charges 6% or 1% and rest is charged by paypal themselves.
These comparisons will vary based on product price, but this is nowhere close to your 5X claim.
The 5X is in terms of the "take" percentage (1% vs 5%).