Also,  try doing a STARTSESS to a virtual port and compare the results of
going to a nailed DTC port.   There are user written applications which
depend on nailed ports.   If HP enhanced MPEiX to allow a STARTSESS to an
IP address, or a HP "FOPEN" of a remote IP address as an interactive data
device... then much of the need for DTC's would fade away.

You can get some pretty good hardened PC's at a low cost.   Now days the
keyboards for HP terminals are made by Keytronix (Spokane WA) and are
basically the same device as you see on an ordinary PC.  You can by small
book PC or thin client boxes for under $400 (monitor extra).  Low cost B&W
VGA monitors sell for about $100.    I.E. you could devise a PC solution
that would still operate in a nasty industrial environment.  So I don't see
the PC cost vs. dumb terminal cost as the main issue.  I think the bigger
issue is the nailed ports and better print page recovery that you get with
the DTC's.