with a mill worth 100k, you have to make a product that will return that investment, as you are keenly aware, within a short timeframe
with 150k even more so
this is still why bars and partials are the profit kings of the dental cnc world. some charge 500$ per implant site for a bar (makes an AO5 kinda costly) and some upwards of 800
you do 3 bars and you made profit that month.
same math for crowns, if it can cost you 10$ in material and 15 minutes of time, then it costs 40$ per hour to run the mill to make crowns. as long as that gets you more than 4 crowns at 200$ each, you've come out ahead by a bit but not by much. times ten pucks overnight and now we're talking some real money. at that rate, you can take weekends off. take a few days of down time if something breaks. the profit is made.
does that make sense for a 1 man lab?
you tell me, you're the 1 man lab.
theres plenty of ROI calculators out there, they all need to know your volume of production, because without it you may as well owe a million, it wont get paid off. everything comes down to production.
hell, you can put in a million dollar mill and pay it off on a 3bars per day volume and pay yourself a measly 80k/yr as long as you can maintain consistent sales. key word, consistent.