"It's unaffordable" can certainly mean "we don't want to pay". It can also mean "Are there enough rich enough people and businesses that can pay, that this can be passed, or can reasonably be collected?"
It is a question of political will, and it's annoying when people lambast that question with criticism as simple selfishness.
Redistribution often hits hard on middle income earners. I'll be impressed should something like this be passed, and the earning figure simply pivots on the median earner instead of gouging earnings from the middle-class.
I wonder at what point Swiss high earners, or wealthy Swiss companies, will move to somewhere like Luxembourg to protect that wealth? Or is it simply not possible in the mind of a Swiss national to do so?