I also use the pill bottle method. When filled, we have a Sharp's container at schoolI will slip them in.
As far as the cost to dispose of the containers, it is outrageous but a necessary evil.
At the animal shelter, I scheduled the guy to come once a year. At the most, he would have to pick up a box that was 3 cubic feet or about 30"x30"x30". It would be filled with as many full Sharps containers as possible. We were charged over $400 for this one box. Then, you have to turn around and buy more Sharps containers to fill. Yep, it gets expensive.