As a BMW F10 (previous gen 5-series) it’s true that BMW maintenance cost are higher than other Japanese or American luxury brands. I think I averaged about $2000-3000 a year on maintenance for wear and tear items (battery, brakes, shocks & struts) once the warranty ran out on my BMW. One of the biggest problems is that parts and labor is fairly expensive and it’s often difficult to find qualified independent (non-BMW) shops that are willing to work on BMWs. When I previously owned a Lexus, most of the parts were shared with Toyota, so I could take it to any Toyota or Japanese auto shop and the mechanics there were willing to work on it and the maintenance cost per year was about half of what it cost to own my BMW.
Just a heads up a 10 year old BMW with more than 100k miles isn’t going to be cheap to run or maintain. Based on my experience as the owner of an out of warranty BMW 528i I would budget anywhere from $2,000-3,000 per year on wear items (tires, brakes, batteries, shocks struts, etc.) more if you drive a lot (more than 20k miles a year). You might get by if you have some mechanical skill and can do a lot of maintenance yourself, but if you have to take it to a mechanic, the labor rate will be very high and can easily run into the hundreds.