Have you already tried one of these things or are you just looking before you buy? Honestly, the commercial ultrasonic kits are really not the same as what a dentist uses - the power is way weaker and they mostly just remove surface tartar. The real problem is tartar under the gums, and you can't reach that on your own without hurting yourself, so it's pretty limited as a solution. I get that it's expensive, but spacing out your dental visits and just doing home scaling could actually end up costing you more in the long run if things get worse - it's better to check if there aren't cheaper dentists in your area or some kind of dental plan.