select member,facility,cost from (select mem.firstname || ' ' || mem.surname as member,
       fac.name as facility,
	   (select case when mem.memid=0
	                then book.slots*fac.guestcost
	                else book.slots*fac.membercost
	           end
	    ) as cost
from cd.members as mem join cd.bookings as book on book.memid=mem.memid
                       join cd.facilities as fac on fac.facid=book.facid
where book.starttime >= '2012-09-14' and book.starttime < '2012-09-15') as t
where cost > 30 order by cost desc