My (25F) friend Ari (25F) is from a really rich family. For a rich person she's pretty normal, she has a full time job, doesn't get much financial support from her parents, shares a house with 3 others, etc. - the only way you can really tell she's rich is that she has really nice jewelry, some nice clothes, a new car and fancy family holidays.
Ari prefers to shop at cheap, fast fashion places and doesn't really know much about designers. Even though I'm not rich, I am an avid hunter of second-hand designer bargains. If we each had $50 Ari would rather buy a $50 dress from H&M whereas I'd be rather buy a $200 secondhand Zimmermann dress, wear it five times, and re-sell it for $150.
The other day I went to Ari's place for dinner and she was halfway through cleaning out her closet. She'd received a bunch of designer clothes, purses and shoes for Christmas and her birthday, which she wasn't going to wear. She was also throwing out some old work clothes and wedding outfits. I looked through the pile and there were some really nice brands in there worth hundreds of dollars. I asked if she planned to sell them and she said she would just donate them, because she'd tried to sell stuff online before without success. I thought it was likely this was because nobody wanted to buy her H&M stuff secondhand, and gently suggested that her high end things would do better online. She said she couldn't be bothered doing the listings and "just want to get rid of it" and I suggested I could help list them, and we could split the profit 50/50. She eagerly agreed.
I took the items home, took photos of everything, listed them in specialist brand name forums and groups, and have sold a lot of things, which I organised to post or delivered. So far I've made $1400. When I told Ari I'd be sending her $700 she was surprised but overjoyed and thanked me profusely, saying that she had no idea how much those items were worth.
I told my mum about this thinking she would be impressed but surprisingly she told me I took advantage of Ari. She said I should have made it more clear to her how much her items were worth, and that 50% 'commission' was an inappropriate amount to charge for items worth so much money. She said that after Ari commented that she didn't know how much the items had been worth I should have offered to give her more of the proceeds. I don't really see this perspective as she was fully ready to just donate the items and I've made her $700 that she wouldn't have had otherwise. AITA?