Most heart hardedly agree that DC should be a top priority in any shop and the lack there of should be discussed. But at the same time comparing costs while fruggle is good it shouldn't be the only determining factor. As you well know the cost of not doing due diligence is much higher than most of us want to admit and unfortunately it usually is after it's too late that the issue gets any real attention. When I explored my needs I used calculations based on what experts said were needed for my space. There are excellent books out there that cover this very well. As you also pointed out there are woods and other materials that are a higher concern than our "normal" woods. I recently worked with some Cambia for the 1st time and read all the warnings related to that wood. Every piece of DC equipment was used as were the masks. The sawdust off this 6/4 Cambia was as fine as cocoa and very easily airborne. Eye protection was a must as well. To see just what was caught in the air filtration system was amazing as it just didn't seem to be that bad when working with it. Imagine those sharp edged particles in you eyes and lungs. MDF makes the same mess when cut.
Most of these units are rated for area that they will be covering. It may be needed to have multiple units for some large shops and they need proper maintenance to function properly and filter changes when needed. And just like my HVAC customers before retiring,don't skimp on the filters as they are the heart of the system and determine if the system is truly doing the job it was designed to do. Don't forget to clean the bags as well. Out of sight, out of mind. There are simple water gauges use can install on both sides of the filters to show you when they need changing. They read the static pressure difference. Basically you're not moving the full volume of air if the filters are clogged up. And for that matter you should inspect and clean the squirrel cage fan when there's any buildup of dirt on them as that changes the fan air curve as well and reduces flow. A very early lesson in my HVAC career was when I was working on a 30 ton air handler at the phone company. This system had 2" pleated pre-filters and 4" pleated filters. The complaint was it was stuffy and the fan was running constantly. I went up and looked at the air handler and it sounded OK but the amp draw on them motor was way low. I turned the fan off to look inside. My 1st thought was a frozen or blocked coil which was technically correct but it wasn't frozen over, or a dirty coil, or obstructed by anything physically on it. I pulled one of the 4" filters and looked, not too bad but probably could use changing, there were only 16 of them. For some reason I closed the door, turned the fan motor back on, and took another amp reading across all 3 legs. Still low but this time I tried to open the filter door with the motor running and I had to put my foot on the unit and use all I had to open the door. I'm not a small out of shape person, at least not back then. The air rushed in taking my by surprise. I took more amp readings and they were where they should be. Another shutdown and now I pulled the pre-filters. They looked as if they were solid core. A quick trip to the supply room and several boxes of filters was what it needed to get the airflow back to normal. You really don't want 40 females complaining about their comfort level, actually about anything....
So it behooves us to look at our shop, take some measurements and see what we need. If you're unsure call the company or look on their website for proper use and sizing. If it isn't there and they can't advise you I suspect you have the wrong company, call someone else. While agree price is important, and I do research almost every tool I buy to make sure I'm getting a good deal, almost too much sometimes. But I want quality, reliability, and support. It should do what it's designed to without fuss and be serviceable. And when it comes to air quality it not only you but your family as well, like 2nd hand smoke. Tom has given you more then enough real life reasons to follow through.