A lot of people are disliking the prince for being scheming, manipulative and only doing something for his personal gain... but that's exactly what the MC is doing, too. She's scheming and manipulating the people around herself only for her own (and her brother's) interest. She doesn't care about anyone in the royal family beyond from what she can gain from them. Besides, scheming and manipulative is pretty much standard for royalty if they want to survive, he's actually being pretty straightforward with what he wants and what she'll gain from it.