Paying mid-hi $xx,xxx for a .biz domain is speculative at best, IMHO. I can only find 3 .biz sales above $10k on NameBio (only 1 on dnsaleprice) and that includes Loan.biz at only $11,350!
On the other hand, if .biz popularity explodes they might be able to flip it for a profit, but I doubt it will happen in the nearest future.