I was browsing through the main manufacturer's web sites today and found:
Cannondale - no tandem listed on web site?
Comotion Primera $3,995
Santana Arriva $2,995
daVinci Grand Junction $3,495
Looks like some pretty good options out there. Components vary with daVinci using Tiagra shifters and Comotion's & Santana's suing 105. While not top level when I have ridden 105 and Tiagra for short distance they seemed to function well.