With a disposable that is pennies a part, it does not require a "new machine" with every tattoo. And your are correct that most of the time the carts don't leak and the Hawk with the built in seal prob never leak. But I have seen them leak and I can see cross contamination by moving the carts when changing them. This is not the cure all that everybody needs, but so far the product is being very well received by many of those who have seen it.