Well, you could always ask her. Say something like, “Honey, is it easier to be in a relationship with me, or would you rather hold out for someone who likes you a little more?”
It’s true that more beautiful, higher maintenance women sometimes come “with a cost,” as you say. Perhaps they are used to being treated like a queen, and will demand that kind of treatment from you. Perhaps they have their pick of the men and will choose the higher bidder. If you are good-looking and wealthy, you may be able to land one of them. Sure, it’s costly, but life is all about choices, isn’t it? If beauty is pretty high on your list, and you can afford it, dump the chick that loves you and go for the status symbol.
On the other hand, ladies that love you, that doesn’t happen every day. The girl you’re with might not be the one for you, but I will tell you that it’s easier to find someone hot than someone willing to put the work into the relationship and who loves you back.
Bottom line: if you’re not ready to settle down yet (you sound young), date around for a while. Date beauty queens (if you can get them to give you the time of day), date homely girls that are nice, date the average. (Most people are average.) And then when you have that out of your system, and you don’t feel like you’re missing out because you’ve been there and done that, then find someone who you love who loves you back. Perhaps by then, you will notice that looks fade, or aren’t as important in the first place, and that what matters is how close she holds you in her heart. And by then, you will be ready to give her (whoever she is) the kind of love she deserves, right back.