What quantifies as "not many doors"?
We use four shapers currently for making doors. I don't feel we build that many doors. If I were to ballpark, we've probably done around 1200 this year, including the five piece drawer fronts. But it wouldn't be profitable at all for us if we did it on one or two shapers. The change overs are expensive enough just swapping heads with no fence or spindle adjustments.
Unless you can spend the money for NC controlled everything and an hsk electro spindle, changing gears for different processes takes a lot of time.
I've still got two Powermatic Model 27 shapers. They're both in need of retirement. When we stepped up to heavier shapers, those two PM's got setup solely for coping rails. The tighter tolerances and heavier build allowed us to swing bigger heads at a lower rpm which delivered a much smoother cut and better fitting joint.
Cheap shapers cost too much. Can you do it with cheap, light shapers? Of course you can, most of us probably started there. But better tools, in my experience, are always worth the price of admission. I wish I would've been smarter and poured a little more money into that much sooner than I had.
The used market isn't like it was in 2012, but there's still really good used equipment out there for a lot less than new.