They are expensive! The contracted insurance prices vary a little bit and there are 3 main manufacturers. But I'd say it's a safe bet to plan on about $10,000.00 give or take, depending on who you buy from and what kind of a deal they might be willing to make for a cash purchase without insurance (I'm assuming that's what you are asking for)
They do show up for sale once in a while on places like e-Bay and some other medical sale sites (used) for a whole lot less if getting a new one is not an option.
I would recommend calling each one of them to see what they say.
The manufacturers are:
The Vest, by Hill-Rom 1-800-426-4224 <a target=_blank class=ftalternatingbarlinklarge href="http://www.thevest.com/
">http://www.thevest.com/
</a>
The En-Courage system, by Respirtech (800) 793-1261
<a target=_blank class=ftalternatingbarlinklarge href="http://www.respirtech.com/about.htm
">http://www.respirtech.com/about.htm
</a>
The Smart Vest by Electromed 1-800-462-1045 <a target=_blank class=ftalternatingbarlinklarge href="http://www.electromed-usa.com/index.html
">http://www.electromed-usa.com/index.html
</a>
I have a little bit of info about vests on my blog - for very detailed information about the Respirtech go to sakasuka's blog page.
There is not really a limit to how old you can be to use it --the question usually is how soon they can start - which is typically around 2 years old. A 12 year old would not be a problem at all - they are usually considered a lifetime purchase