You are right, No.1 is the most valuable (except, possibly, No.0, but 0 is, normally, not for sale).
logically - it is also the most expensive - its price not known until the entire Issue (edition) is produced and distributed.

The answer above was posted on 2021-01-31, it was true then but now it is not.
Under our "magic" formulae of ›Counted (CE) and ›Versioned (VE) Editions there is no Number 1, anymore.
And, by the way, they are no longer called DCDs but CEAs and VEAs. Each has a unique six-digit number, the value of each is not easily determined, as they might differ to various degrees. Overall, and over time, the value of each CEA or VEA is likely to grow. They are all worth at the launch 100 or 150 CCUs before the acquisition price climbs (or not).