YTA. I understand that maybe you were looking forward to him being extatic about the laptop you chose, but the laptop you chose simply is outdated for many programs in terms of processing speed. Laptops require research to choose as one size doesn't fit all. If ge hadnt been appriciative of thr gift I couldve given you the benefit of the doubt, but 8 gb ram makes "giving it a try" pointless. My old 11 year old Toshiba laptop, which lags incredibly, has 8 gb Ram, and the only thing I use it for now is YouTube and occasionally Word. You made a mistake, which could be easily rectified by sending it back, but instead, you took back the laptop and regifted it to your sister. And trust me, even she is going to realise that that is a slow AF laptop sooner or later, especially as the memory gets more and more tasks to deal with. You seem to think you can make this gift work for you as a gift giver, rather than making it work for the original person you got it for.

This is not the equivalent of someone not being grateful or saying they didn't like the gift when they opened it, it's the equivalent of someone receiving clothing they like but it's 3 sizes too small. And instead of exchanging it, you're insisting that he try it out anyway, is in poor taste.

As a side note, Macbooks are expensive, even compared to windows operated laptops. I usually buy my Windows laptops around the 1000-1500 price range, but if you want to buy a good Mac book, it usually costs a lot more. Especially with newer specs. And if you felt spending more was too much, you could have simply told your BF that you could spend it back and he could pay the change to get the laptop he wanted. That would be fair, and everyone would have been happier.