The efficiency I'm most concerned with is the printing time - Turning up the fill density isn't off the table, but I'm hoping to keep myself under a 36-hour ceiling between the top and bottom prints to give me the best opportunity for print turnover as well.
What you want is precisely at odds with reduced print time.
Your options are either build a small print farm or look at other (also expensive), alternatives such as casting silicone. There is no getting around the fact that low volume manufacturing is costly and the faster you want it the more expensive it will be.
If you're going to be doing manufacturing with 3d printing you need 3 things; speed, reliability and multiple printers.
Most printers are quite frankly, extremely slow and unreliable. If you can't go faster, get more, this is how most print farms operate. More printers mean more maintenance so you REALLY want something reliable with low maintenance. The fix for slow print times is more printers and bigger nozzles, a bigger nozzle will alter looks, sound, tolerances and strength, requiring a whole new round of testing but your cheapest option.
Tips for a mini print farm..
Many will say Prusa is a good choice, and while Prusa does operate a print farm, from experience, that is actually not the best option. It's a good printer but even it is high wear/high maintenance compared to some higher end (including open source) printers. Prusa has a lot of people running their farm but their farm is partly promotional, it helps drive printer sales, yours is not, you want as little effort as possible. Parts and design matter a ton when you have a massive duty cycle. Some printers run rings around Prusa in terms of speed and reliability however it does come at a cost but that gets reimbursed over time through less work, faster prints and parts lost. Basically look at potential wear points, sensors (and types), and top end parts designed for high wear, every wear point is a potential source of failure. Also, pro-tip, get rid of EVERY connector you can on the motion assembly, they are notorious for being a weak point.
Something like an Ender is going to run you ragged in volume with slow print times and high maintenance... An Ender will run half the speed of a Prusa, a Prusa will run half the speed of something like a high end coreXY. Maintenance is similar with a good corexy needing FAR less work. Other than cleaning my print bed my printers go thousands of hours @ 100-200mm/s between maintenance and usually wear a hole though the feed tubes or wear out a hobb before anything else has a problem.
Oh, and lastly, consider a dedicated print room (as in spare bedroom or garage), do some tests for various plastics to see your reaction and consider some sort of hepa filtration. Some plastics, including PLA give me headaches so I either need to run a filter or choose my plastics carefully. I do both in a separate room.
Expensive? Yep, welcome to manufacturing.