I was 100% self pay, so I negotiated 10% off for paying in full up front. Caveat: Make sure "in full" includes everything. Retainers, finsl X-rays, etc. Also, make sure there are no bullshit charges for breaking anything along the way. Finally, office atmosphere and activity level are something to consider. My ortho is a sole practitioner, has one assistant and one receptionist. I never wait. I love her and recommend her to everyone I can.
DH went to the ortho his dentist recommended, he did not want to shop around. It was a fucking factory. Never saw the same tech twice, constant turnover of office staff, lots of kids, extra charges for everything. Cost nearly three times what mine did. He had some insurance, so we paid in a couple of big chunks.
His ortho rushed him through treatment. Six months later, after dutifully wearing his retainers as directed and then some, he had to have them put on again. (He was not a candidate for invisalign.) Then a new set of retainers afterward. The ortho wanted to charge him for the new ones, but a polite and firm conversation was had. Needless to say, we do not recommend him.
That said, we're both pleased with the results and consider it a worthwhile investmant.