My 2 cents:
At the time, it was not.
Now, used Coolscans are overpriced for sure; for lack of competition. 🙁
Because scanners are subject to wear and ageing.
Your lens/filmcarrier distance may be perfect now, but after a few years and many carriage travels, who knows?
A lens unit with variable focus can always be refocused to compensate.
Then there's the issue of temperature variations (materials change their size with temperature), so your focus may be perfect at 18 Celsius but not at 35 Celsius.
Or maybe those Plustek are so well designed and built, and the materials used are so top-notch, that they'll never have any departure from perfect focus distance year after year. That would be great.
Still, the OpticFilm 120 has no adjustable focus, no adjustable RGB exposure, no single-pass multisampling, and it costs Eur 2000.
I won't call it overpriced, but not really a bargain.
Again, lack of competition. 🙁
Fernando