If you are charging just enough to cover application, increase your price a bit for removal to cover product cost as well as your time.
We charge $10 for removal at our salon. Our clients are removing their Shellac on their own because they don't want to pay it. We are losing money.
I recommended, as did our CND Educator/Ambassador, that we increase our application charge by $5-$7 and NOT CHARGE a separate removal fee. The $5-$7 increase would more than cover our product cost. It would also prevent our clients from damaging their own nails from improper removal.
More importantly, it would prevent these clients from bad-mouthing Shellac for having ruined their nails because of the damage these clients were doing from their own improper removal.