I really could use a computer at home for school. Maybe my summer job money could go for that? Could we swing the monthly phone charges? Etc. etc. But be prepared to be graceful if they say no.
Or if it's a values thing you could just start with I'm really sorry I yelled at you, and then skip to the 2nd paragraph.
I don't know how your fights with her usually end, but most parents would be stunned by a follow up like that! Good luck!
In the longer term, for your depression about this, you might want to do some volunteer work with some kids who will make you appreciate what you do have, and help you strengthen your values about what really matters in life. If you always look at the people who are better off than you (and unless you are one of Bill Gates' kids there always will be someone better off than you!) you lose perspective on where you are on the totem pole. See if you can give a hand up to kids who don't have what you do...maybe volunteer at a homeless shelter or food pantry.
Won't hurt your college aps either, and maybe someday you'll have made enough to be helping out your parents financially as well as that same shelter...following in the Gates give back tradition.