If I can source the same stents for cheaper than the hospital bills me, they should be required to erase them from the bill and accept them as material replacement.
It's not as if medical supplies are unavailable to the end consumer.
https://www.esutures.com/product/0-in-date/41-boston-scienti... Here are the stents available for under $1000.
When I had a broken finger and was uninsured, I was charged ~$40 for a finger splint that costs $7 at Walgreens (yeah, the very basic one made out of aluminum and blue foam).
Also, a word of advice - never ever pay what you were sent from the hospital right away. I personally throw most medical bills in the trash and wait until they call me, then negotiate it down to a fraction of what was billed, offering to pay in cash.