So to twin a spell, that would be 4 spell breakers? Or 2000gp (assuming 500gp each)
Yes. The choice on when to use a feat and when to use Spell Breakers to do something would be up to your own optimization needs at the time of casting a spell.
Twinning with a spell breaker does not affect the spell level slot, thus the spell points needed to cast, since it is an external factor.
A spell breaker has never had the ability to twin a spell. At least not in anything I have seen written. Since they were adapted into 3.5 and 10e we have played loose with letting them emulate a feat. Thus the ability to twin was introduced.
During @dwarf’s game on Friday I played with those rules, but really looked at the benefits. So when it came to your game on Sunday, I was doing it this way to have a comparison for myself.
I’m not seeing a huge issue with 1 spell breaker per level adjustment of the feat. I’m always open to discussion and counter points.