Everyone is allowed to shape their lives how they see fit, they can let it go whatever way, good, bad, waste it, mess it up, even. All I would say that at the end of the road, on your deathbed, you will not think back of how great it was not to be willing to leave that nice house for all those years, or what a fantastic decision it was to hang onto the street with that mortgage-free house. What matters at the end of the day is the quality of life, the laughs, the joy, the warmth, who you shared it with, your loved ones. And at that point you would have spent a good portion of your life sharing your living space with someone you are - in best-case-scenario - detached from, - worst-case scenario: completely despise, actively hate. If that is the price to pay so one can afford the premium sourdough bread instead of the boring bloomer, I would want none of it. Leaving the fancy house, taking your side of the money and having to be somewhere smaller as a result, but not having to be with someone who actively chose to betray you, your trust and everything you guys built together? Yeah, that would be fair to me. Being on your own will always and forever trump being with the wrong person - and in this case, it's not even being "with", it's being next to, in the same living space. I keep saying this, but we have one life to live, and spending it this way is well, definitely a choice. Taking away the possibility to find happiness on your own, or heck, even build something new with someone, if that is something important.
And don't forget children - When there are kids in the picture too, don't think this setup is not damaging them. Growing up in a setup where it's normalised that their parents dont love each other, please don't think they don't sense the nuances of it. Heck, if they grow up with this as normal, it could lead to them living a life like that later on. And ask yourself, in all honesty, would you suggest to your own child to stay put in a relationship like that? No, no you would not. Yes, daughter, stay with that serial cheater pig, at least you get to go to Italy every Summer.