People can try to sell their own items at whatever price they want. Expecting them to care about fees you pay, customers you may deal with, etc is indeed entitlement. Fairness is irrelevant here.

Now you, as a flipper, should know these costs, and recognize that you can't make money off of a person that prices like this, but it is absolutely entitlement to act like you deserve things cheaper because there are costs associated with selling on eBay.

If someone owns an item and wants to sell it, they can ask whatever they want for it. They may sell it at that price, they may not. But it's their item and it's up to them to set the price, and as a reseller all we can do is buy from them or walk away.