How much does the cost of black triangle treatment with uncut laminate be?

My teeth are fairly straight, but there are gaps between the teeth where the gums and teeth connect. Because of this, I look a bit older and I always cover my mouth when I smile. It looks like a black triangle, and I heard that veneers are the solution to fix this. I don't like the idea of grinding down my teeth, so how much does no-prep veneers cost? Are no-prep veneers significantly more expensive than regular veneers? I'm also curious about the treatment duration and cost.