We've developed a full breadcrumbs system for Elgg for our client. The mechanism sets breadcrumbs for all pages based on standard Elgg architecture. This makes Elgg navigation a lot clearer and more usefull. We will soon implement the mechanism on our site.
Mechanism still requires tuning to every website, that's why implementation costs are ~500-1000$, based on complexity of the website.
If you are interrested in using this plugin on your site, please let us know at info@elggdev.com