You walk into a celebrated high class restaurant, and at the bottom of the menu, it reads "Human meat steak. $10,000". You ask the waiter who fetches the chef. The chef comes out and explains that after decades honing his craft, he feels like he's a master of his craft, and now he'd love the honour of cooking a steak taken from his own body. If anyone purchases the steak, a skilled surgeon will remove half a pound of meat safely from the chef, who will then prepare it for you, and the chef is visibly keen to serve this.
As a vegetarian, I honestly don't feel that this would bother me, if I had money to spend, the only reason I wouldn't go for it is that I'd worry the chef would come to regret giving up chunk of his ass or leg or whatever, and I'd be partially to blame, or that the chef was not thinking straight otherwise.
This situation kinda reminds me of John Locke talking about slavery. He says that for some rights to be truly inalienable, that people themselves should not have the ability to willingly surrender them, such as by willingly selling themselves into slavery. Now, yes, John Locke owned stock in a slave trading company, so he's a hypocrite in that regard, but I digress. I feel like this is one of those things where people shouldn't be allowed to physically sell parts of their body for consumption, as "not being eaten by other people" is one of those inalienable rights we should have as a society.
It actually gets worse.. i saw this post here on lemmy.
When someone replied to her exactly that, she said she "didn't always consent because she doesn't always feel like it but she does it for her baby, is that still vegan??".
Only if you define vegan as to strictly avoid any animal product (and define humans as animals). A somewhat looser Definition says to avoid animal exploitation.
So a product made by a non-domesticised animal in a natural way - e.g. Penguin guano - could be seen as vegan. The animal produces it anyway and the product isn't won through keeping the animal captive and / or "stealing" from it.
After all I wouldn't be too strict with definitions here.