The easily enumerable part is loaded salary costs (salary + overhead
for offices, machines, etc).  Producing ANSI CL [1986 to 1995] took a
bit over $400K, if I recall right.

The costs of a zillion people traveling, of the timeline being years
long, of people sitting at desks answering email and reviewing
hardcopy, etc., are hard to measure.  I'd say probably that comes
close to doubling it...

None of this counts the cost of the community "accepting" the changes,
meaning of each user reading new documentation, of vendors making and
testing new implementations, of deployed products looking for and perhaps
even debugging incompatibilities (this cost may be present even if the
incompatibilities won't be there, since one has to at least check).
An analyst report I saw at Symbolics once for a fairly modest set of
incompatible changes (that is, small in number but pervasive in nature)
showed that target customers often pay upwards (sometimes way upwards)
of $10K per customer to accept such releases...  This aggregates to ENORMOUS
community cost before any new benefit is realized.  

Before making changes, one wants to believe they are going to overcome
these costs.

Layered standards are another matter, but require no change to the existing
core.