Are these "leather cups" you're talking about these "ear cushions" (https://www.bose.com/en_us/products/headphones/headphone_acc...)? If yes, then that's only 30-40$, which does not seem unreasonable for a product you use so intensively? I replaced mine after about 2 years. I remember the sound insulation being a _lot_ better afterwards.

I have the same experience on the battery: my pair is almost 3 years old and I can go about 2 days of work (~12 hours) before I have to charge them.