3 weeks post op, 620 cc right breast, 630 left breast. Mentor moderate plus saline. Was I botched or is this normal? (Photo)

At three weeks you are about 15 percent settled, shaped, softened, dropped and fluffed. "Drop and fluff" refers to the fact that as the skin stretches and the muscles relax, the implants move down and out slowly – about 1 percent a day. It’ll be about six weeks before they even begin to settle down, but they’ll be close to 80 percent settled and softened at three months. Watching their progress is like watching your hair grow. You don’t see a difference in your hair growth daily, but all of a sudden you need a haircut. 
Be patient after surgery. Give yourself a few months before making a judgment about your surgical results. You won't know the outcome until then. 
Dr. Ted Eisenberg, Board Certified Plastic Surgeon and Author

With this size of implants everything will remain tight for some time. The implants need to drop and soften and the skin needs to stretch. Things will improve

First of all, you were not "botched" just because you have some asymmetry; this may have been partially present preop, or you may have had things look great on the OR table and be healing and settling differently. You also could have capsular contracture or other issues making the two sides heal differently. At three weeks it is very early and most surgeons will advise you to wait at least until the 3-4 month mark. Sometimes the soft tissues swell differently on the two sides, or the pockets that looked pretty symmetric on the table are not healing the same way. It is hard to achieve perfect symmetry when such a thing does not generally exist in nature, but you should at least discuss your observations with your surgeon and follow guidance on any maneuvers suggested by the surgeon while your result evolves.

I'm sorry to hear about your concerns after breast augmentation surgery.
There are many variables when it comes to how much breast implants will "settle";  the main variable in my opinion will be exactly how/where the breast implant pocket was dissected.  For this reason, your plastic surgeon will be your best resource for accurate assessment, advice, and/or meaningful reassurance.
 
Generally speaking, breast implants will "drop" into the pocket that was created during surgery. The rate of breast implant "settling" may depend on factors such as size of breast implant pocket dissected, tightness of the overlying skin/muscle layers, and size of breast implant utilized.  Some degree of asymmetrical "settling" is commonly seen.  As the breast implants "settle", the lower breast poles will round out, and the nipple/areola complexes will sit higher on each breast mound.  Often,   as breast implants fully settle, breast symmetry improves.
 
 Best wishes for an outcome that you will be very pleased with.