They dont even have to be expensive. We spent like $200 on my wife's Sonicare. I have some cheap toothbrush I got on Amazon for 30 bucks. They both brush just as effectively.
If you're like me and you can't do string floss, try a water flosser. It's what got me started flossing. No dentist will tell you it's just as effective as string floss. Any dentist will tell you it's better than not flossing at all.
Plus, my breath stinks a lot less.