It is refundable, not sure about the timeline.
My guess is that it’s probably 125-150% of the cost of a regular
DCL cruise which turns many away from wanting to go.
I have probably been on 13 of them during my 19 years of
DVC membership. Some just didn’t fit with my school schedule, I taught math at UC, and we were on quarters. My husband has been on fewer, 9 maybe, because he doesn’t think the extra money is worth it but I have always felt the “behind the scenes” talks and movies, as well as the special previews are. Never had a problem finding someone to go with me.