I need a solution to let me use VoIP internet telephony over satellite
broadband. I've read that it doesn't work, but am uncertain. I'll pay
$25 for a solution that lets me use DirecTV (Pegasus) as an
alternative to landline telephone, which would be ridiculously
expensive at my foothills retreat.

i dont how much this would be of help to you.
but you can use this link http://www.idirect.net/technology_qos.asp
and there is a which paper which you can go thru(PDF File on VoIP over
Satellite Using iDirect System).

www.iconnect.com - buy a phone from them and open an account so it
lets you access the landline gateway from your IP connection. Also
incoming.