reason some costs

tsa/howto/conference.mdwn

@@ -117,6 +117,27 @@ Cost estimate summary:
 | Jitsi           | 74 hours  | €54 + 10 hours |                                     |
 | Big Blue Button | 156 hours | €54 + 8 hours  |                                     |
 
+Some observations:
+
+ * Mumble is harder to use and has proven to absolutely require a
+   headset to function reliably
+ * it is assumed that Jitsi and BBB will have similar hardware
+   requirements. this is based on the experience that BBB seems to
+   scale better than Jitsi but since it has more features might
+   require comparatively more resources
+ * BBB is marked as having a lesser monthly cost because their
+   development cycle seems slower than Jitsi. while Jitsi continuously
+   pushes out updates on multiple components, BBB seems to do a little
+   slower release schedule.
+ * BBB will take much more work to setup. it's more complex than
+   Jitsi, but it also requires an Ubuntu, which we do not currently
+   support in our infrastructure (and an old version too, so upgrade
+   costs were counted in the setup)
+ * that, however, might be optimistic: we do not actually know how
+   reliable BBB will be in production. preliminary reports of BBB
+   admins seem to say it's fairly stable and doesn't require much work
+   after the complex install procedure
+
 ### Mumble
 
 Assumed configuration