Well, I certainly don't want to leave anyone wanting... :-)
I put the Slingshot expander on my scanner and grabbed a couple of scans for you:


As you can see, it's a remarkably simple yet effective device made by Prespect Technics, Inc. I picked it up used for $20 back in the early 90's, and only ever used it with an A2090 card. I would like to test it with a GVP RAM and SCSI card I just recently won on evilBay; but I digress. Back to your questions.
The box is fairly common, I think, in where I live from the early days of the Amiga 500 release. I live in Canada, so if you're in a different country, that would explain the difference. I have seen them in much better shape at the local flea market; remember, this one's been hauled from one place to another with my A500 system over the years!
As for price, I can't remember exactly what I paid for the A500 and 1084s; all I remember is that I bought them both from a store in Peterborough, Ontario, after I sold my entire C64 system for $400. It might have been $800 for both. The A590 was an xMas gift, but I recall it being around $200. The 1011 drive was definitely $250. These are all pre-1990 prices.
The "Stand" on the monitor is built into the 1084s monitor; it flips down. An earlier version of the 1084 monitor has two "Legs" flip down from behind, allowing the monitor to "Prop up" on the flat vented spot of the A500 (though it "Fits" better on a Commodore 128).
As for the "Cheese" 501, I'm not too worried about it; as I have acquired a Supra RAM expander with a Lithium battery for free. I may pop open that old A501 to salvage the RAM chips.
I do plan on doing more. So far, I have this, along with
this page which shows my A2000 system and explains how I replaced its clock battery. Eventually, I'd like to have a bunch of material on the A500/A2000 duo (my all-time favourite Amigas) accessible from a main "Home" page.
As for the pictures, they were not retouched...just photographed in a manner to show a yellowed A500 at its best. :-D