Andrew,
Thanks for the post. I, too, am getting ready for the trek
to Boston. Let's see if we can clarify a few things
so that later discussions will have a sharper focus.
1. I am willing to assume that the social value produced by
the machine under discussion is constant. This means
that those buying either cheaper or better machines will
obtain a greater rate of profit than anyone with the
older machine. Should that greater rate of profit become
the general, then in a sense the older machine is "devalued"
despite its constant nominal price.
2. Let's consider the case where machines simply become cheaper.
My contention is that the older machines will be as useful
as the cheaper machines. To be sure, this could cause problems
for the capitalist owning an older machine but even is the
older machine is devalued both by the cheaper machine and
depreciation, it can still compete with the cheaper machine.
Physical durability would set the limit to the life of a
machine if all that happens is the cheapening of machinery.
3. The degree to which cheaper machines present problems is
inversely related to the degree to which the machine has
been depreciated. Hence, in its first few years of life,
the threat is greatest. Note that a fully depreciated machine
cannot be threatened by a cheaper machine.
4. What then knocks the fully depreciated machine out of the
picture? Again, it may be that it physically wears out. Or,
the BETTER machine. That is, a machine with which a capitalist
can earn a greater rate of profit than he could using the
older -- fully, depreciated -- machine. Or, a machine with
which a capitalist can earn a greater rate of profit than
he could using the older --partially, depreciated -- machine
provided that greater rate of profit can be earned even when
the undepreciated portion value of the old machine is seen
as part of the cost of the new machine.
In general, my points are simple. (1) The valuation of machinery and
the concept of moral depreciation can not be viewed without reference
to the rate of profit. (2) Cheaper machines should not the principal
focus when we consider "moral depreciation." BETTER machines are
in reality what establishes the social durability of machinery.
(3) I assume that the social durability is less than the physical
durability of machines. That is, I assume moral depreciation.
Side note:
Related to this is an idea that popped up on the list awhile ago.
"Better and/or cheaper machines presume that better and/or cheaper
machines are used in their production." I do not think this is true
as one could obtain economies of scale in machine production using
the same means of production with a better division of labor.