No, I don't know about "down payments." Most hospitals I work with make full payment, or in the case of MRI, there's one company that doesn't even sell their product -- they lease.
A routine mammo machine is $100,000 to $200,000 (last time I checked), while digital mammography is closer to $500,000. A breast-dedicated MRI will cost a little more than $1,000,000 in most cases.
As for needle biopsies, I'm not sure where your data is coming from. Yes, surgeons fought against needles tooth-and-nail, but that fight took place a decade ago...surgeons lost. There's not a qualified breast center in the country today where most biopsies are predominantly surgical. Maybe in the boondocks, but in metropolitan areas where quality mammography is being done, 90-95% of the initial biopsies are by needle. The reasons are so powerful that "breast surgeons" even had to admit it, and they have fought their way for the right to do "radiologic-directed needle biopsies." So, at many breast centers, the surgeons alternate with the radiologists on the stereotactice biopsy system, and many "breast surgeons" even own their own stereo devices, operating like radiologists.
NO ONE in the past 10 years has tried to defend an old-fashioned surgical biopsy in print or at any breast cancer meeting. Old news. Dead issue. Keep in mind, on occasion, we find something on X-ray that is still best removed in its entirety ("dark stars", for instance, can be a lesion that is hard to distinguish from cancer...the diagnosis best made at low power on the microscope, with the whole lesion out of the patient -- even then, we are doing more and more needle cores on these). Also, sometimes the needle core gives you a diagnosis of "atypical hyperplasis" in which case we proceed to a surgical biopsy, as more serious pathology may be nearby. But the needle comes first, then the surgeon.
Disagree that no doctors are against needle biopsies. Many think that needle biopsies into cancerous region can spread the cancer. I agree the surgical biopsies lost out for several reasons including cost.