The dialysis clinic/company cannot charge a patient for equipment "depreciation." Insurance companies, including Medicare, require that charges for home dialysis are billed per day of use. Medicare pays a single payment for the month of dialysis treatments, certain labs, certain meds, and support equipment and supplies needed to provide a safe dialysis, including home use of an HD or PD machine, dialysis chair, scale, BP monitor, etc. Other health insurers do not bundle these items and instead want dialysis billers to list each item separately per day of use.
If your mother has an employer group health plan that is paying first like it must do for the first 30 months of Medicare eligibility (whether the patient takes Medicare or not), having Medicare Part B as a secondary payer would limit what the dialysis clinic can bill your mother. The clinic would have to accept as payment in full what the employer plan pays as long as it's at least 100% of what Medicare allows for the bundled rate. if your mother has a Medicare Advantage plan instead of Original Medicare, that plan may or may not require dialysis billing for treatments, supplies, and equipment to be bundled. MA plans can charge copays or coinsurance on covered services/items. The maximum in out-of-pocket fees varies by plan, but can be no more than $6700/year or no less than $3,400/year.