It's impossible to weight the factors like you did, but I'll share some thoughts. Generally speaking, I'm taking about the top schools.
1. A low GPA can be overcome. A GPA in the 2.5-3.0 range (below the middle 80% for most schools) will not prevent you from being considered, though you will have to show you can handle the work in other parts of your application. Quality and difficulty of your school(s) factor in as well. If your school was really difficult to get into, and was highly competitive, they will take that into account.
2. A low GMAT cannot be overcome, for the most part. A GMAT below 650 (about the middle 80% range for most schools)
will keep you out, unless you have something very, very substantial in your profile. If your family is a huge donor, or if you are an underrepresented minority, you might be considered with a sub-650 GMAT, but if not, then you're wasting your time. A GMAT over 750 is nice, but it won't get you in. The higher the better on the GMAT, but it will only go so far in addressing other weaknesses; and primairly a very high GMAT is most useful in offsetting a low GPA.
3. You weight Recs at 20% and GMAT at 10%. There is no way on God's green earth that Recs are worth more than GMAT. Recs have very little upside value. I heard again and again last year that schools expect virtually all admitted students to have stellar recs. The reason is that applicants choose who writes for them, so the only thing that can really happen is that they get a lukewarm or poor Rec that torpedoes their application. I think Montauk states in his book that maybe 10% of applicants get poor recs without even knowing it. The bottom line is that if your recs are anything but stellar, it will hurt you; but it's hard to imagine what it would take for a rec to really help you, when compared to other applicants.
4. The interview means nothing unless you are invited. Of course, some schools (very few now) interview all-comers. Once you are asked to interview, the value can vary a whole lot. At Duke and UCLA, for example, you interview with alums and students, they work off a script and the entire process feels very sterile. It's hard to imagine the interview having much weight. At Columbia, you interview with an alum, and experiences will vary, but my recommender disclosed that even when he turns in stellar reports, Columbia doesn't really follow. The rumor is that at Harvard, if you are asked to interview your chances are probably at least 50-50. At Stanford, the rumor is that the interview is more or less fluff. So, interview weight depends on the school, but for most places it is a good indicator that your application has made it to the next step.
5. Diversity can make a huge difference. Depending on how under- or over-represented your group is, diversity could mean as much as 100+ points on the GMAT, a full point of GPA, and a whole boatload of work and extracurricular experiences. We'll just leave it at that.
6. Essays are definitely worth a lot. As mNeo pointed out, if you're done with the GMAT, essays are the only remaining thing that you have control over. At this stage, you can't do much about your GPA, you can't effectively start new activities, you can't change your profession. You might be able to practice interviewing skills and so forth, but really, essays are the only thing you have a lot of control over, so in that sense, essays mean everything to your application. Of course, if your history to this point (experiences, scores, etc.) do not measure up, then it won't matter how well you write your essays. Another thing to consider about essays is that application review procedures might not allow for the greatness of your essays to shine through. You essays might be reviewed by some student with something else on their minds, or it might get a quick read-through, or whatever. Essays are unlike the hard data in your application because you need someone on the other end that recognizes how awesome they are. Which leads to the factors you didn't list...
7. Your work experience and activities will be key elements of your application. In order to have great application essays, you'll need good writing skills and great content. It doesn't matter how well you write if you have nothing to talk about. On the other hand, if you have great experiences but only average writing ability, schools will probably give you the benefit of the doubt. If someone works at a blue-chipper like Goldman or Google and has been promoted ahead of schedule, etc., then average essays will be fine. An assistant manager at 7-11 could write something worthy of a pulitzer, but that's not going to change the fact that his experience comes up short. You need content to have great essays, and that includes all the stuff you've done in your life. Of course, it doesn't hurt if you're a great writer and can spin great stories about your experiences.