Me and one of my co-workers moved and old Dimension PBX up that many stairs by ourselves with an appliance dolly. I believe it weighed about 800 lbs. We were in our 30's and a heck of a lot stronger than we are now. When we put in in the bed of an S-10 pickup truck, I thought the bumper was going to hit the dirt. A gross overload for the S-10. Of course balanced on an angle and on the dolly wheels, most of the weight vector is down and supported by the wheels.
Four of us strong men picked up an old PBX that weighed 600 pounds out of a "doghouse" on the roof and carried it across a tar and gravel roof to the edge and let it down a set of stairs. We used 2x4 's run thru the pbx frame with cushion pads on each corner to rest on our shoulders. We left footprints in the roof though. 150 lbs on your shoulder is about all I wanted. It is amazing what you can manhandle. Of course injury is always possible.
We moved PBX's "back in the day" when they were made out of steel and not modular. We did it all the time both the old ones out and the new ones in. Eventually they became modular and smaller. And smaller. Now days a PBX is something that looks like a modular router and you tuck it under your arm, or it doesnt exist in physical form, just a DVD you load into your own server. A DVD sure is lighter to carry.

Or you just download the software on a USB stick and pack that into the door to load on your server. I remember the "good ole days" but I am not sure they were all that good.