Howdy Pete,
You make a very good point on the price. It seems to come down to many people buying a pig in a 'poke' compared to making a purchase from a known entity at a known level of quality.
Many of my purchases of old tools have been "pigs in a 'poke'." Many turned out well and some not so well.
It seems the price of purchasing a Stanley #45 has dropped a bit over the years.
One needs to recall the "floral motif" was gone from the #45 by the time the adjustable fence was part of the plane.
The cost of modern manufacturing will always be higher than the cost of finding something made ~a century ago. One thing to remember is it was almost a day of celebration when one of my Stanley #45 purchases arrived with any blade sharp enough to go to work. This hasn't bothered me. One of my favorite pastimes is fettling old tools.
For some the frustrations that come with getting an old plow plane to work well isn't worth the savings in dollars. To others like myself, it isn't an experience of frustrations, it is an experience of learning.
Of course the wood doesn't know the difference. My bet though is someone who has never used a plow plane could produce good work from the Veritas Large Plow Plane just as quick and possibly faster than me with one of the #45s you mentioned above. This would be especially true if the blades from the #45 needed any sharpening work.
The Veritas Large Plow Plane has many improvements over the older plow planes. Many users like us will be perfectly satisfied with our older versions just as newer users will be very happy to have a modern creation in their tool cabinet.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)