dental implants might fail, but if they fail, depends on the doctor, and also the company they work with, they can give you a warranty, not in a 100 % but , at least on the implant replacement, there are cases where you can show the patient the strength of the implant with primary stability, and months later it comes loose,
if your doctor showed you the primary stability,
then is your doctor ethical point of view to give you a solution,
waiting time 3 to 5 months and later on , you can re set them again.
Only death and taxes are guarranteed
While it may be "good business" to cut a break or find middle ground, nothing is 100%. There are many reasons why an implant may fail, some of them have nothing to do with the dentist. Placing blame usually harms everyone and is not productive, and in this case may be debateable with no clear fault to place.
Sometimes implant manufacturers will donate a new implant within a certain time frame. Perhaps a discount, but not 100% free, is possible. Ultimately it is up to each dentist how they want to run their business and there is no obligation to redo the implant at no charge.