Long ago I gave up on using high quality brushes. Canvas and paint I always use an artist grade... but brushes, no. Dollar store for some mid size ones, fine liners are a splurge, but necessary.
I tend to kill them by either scrubbing them down to nothing on the canvas or I get distracted and leave them to soak by accident.
It doesn't bother me much when I do it to a $1.00 brush but when it happens to something I paid $8.00 or more to.... yikes!
My son's teacher loves me. I tend to give her fairly large used brush donations during the year. They can use the better ones for painting and the shabbiest ones for glueing things. I feel less guilty for my brush killing tendencies.