I agree. People ask how I can tolerate the weight of the 645 system. When I ask what they routinely haul around, especially those shooting Canikon 35mm systems, it's not unusual to find out their net weight is comparable to or even heavier than what I carry. I typically use a ThinkTank shoulder bag that isn't too large, and becomes uncomfortable on the shoulder if I over-stuff it. So I (mostly) don't do that. Folks who shoot out of camera packs often simply have a lot more gear stuffed in there.
In June, I was 3 weeks in Iceland with a pair of 645D's and a selection of 5 lenses. (Well, one of the 645D's had a shutter failure near the beginning of the trip, so it stayed in luggage.) I carried and used the kit almost every day; sometimes for long hours. This included a 12-day stretch where the shooting mostly went on for 12 - 18 hours a day outside of meal breaks (and rain breaks). Would I have liked to have a lighter rig? Sure. But I wanted to shoot and get the images from the 645, not something else that didn't have the same shooting experience or resulting image "look" and quality.
So I live with the weight and sometimes dial my lens selection down to a different subset in the bag, on given days. It's eminently doable. Oh, I'm no physical 1-percenter, either. I'm probably well past my midlife crisis point even before buying into the Pentax 645 system
, and I'm not in the shape I could be (arguably, "should be"). Like others have said, I like and want to shoot the Pentax 645 system more than anything else I've used in digital since around 2002. Weight savings is not the reason I pick up the D or the Z.
Even the purchase price of the kit is something that I just need to work around. Most of my kit is older A and FA lenses, and I'm happy with them all. The DA 25mm was a unique optic with capability I needed and couldn't get in any other package, so I added it. I didn't particularly like the D-FA 55mm and the FA 45-85mm was optically more than good enough @ 55mm, so I passed on the D-FA 55mm. It wasn't mainly a price issue, the lens just didn't do anything for me, even if it had been $50.
I do like the D-FA 90mm a lot but can't justify it right now so I'm holding off. The new DA 28-45mm is also pretty unique, and if it's good enough it might eliminate the need for my A and FA 35mm lenses. (Not the 25mm, though I may not need to carry the 25mm as often as before.) Either way, the new zoom is very attractive for my type of work so I may have to plan it into the mix... in which case I'll just deal with the weight and cost and go on being happy to shoot the system and get the results it gives me.