How much would it cost to produce 1,000 copies of a book that’s only 20 pages?

I suppose one approach might be buy yourself a hand crank mimeograph and go to it. I'm going to say $300 bucks this route. Half for the machine, and half for the paper and ink. That would be kind of fun, because it would be like you were producing some old school underground newspaper. 

That being said, printers who do dissertations and the like can give you a quote on this. 

Twenty pages isn't a book.

For something like that I suggest using Staples.

https://www.staples.com/services/printing/copies-d...

Call the Harvard Book Store in Cambridge, Mass. They do exactly what you're looking for.

Too many variables......print , hardcover, binding type, colors or B&W, ....paper quality.......you need to tell the printer all that to get an accurate estimate. 

If you sell a devotional or recipe book you could get away with that 

Cost depends on the page size, the type of paper, the type of cover, whether it has photos and illustrations and how many colors are required. When you determine all of those specific factors, we can give you a ballpark price. 

Hardcover or softcover? Locally at a print shop or sent to a book manufacturer? Remember there's shipping costs involved then.  You need to give us more information,  it's impossible to quote you anything. 

I did a print run of 200 at Office Depot, of my comics, 40 pages,  softcover,  double sided and printed in black and white.   I did the stapling.  Anything over 50 sets and they gave me a discount.   It came to $1.48 per unit, my retail price was $5.  Usually the more copies you get,  the lower the price per unit.

There's all kinds of publishing.  Since you have the number of 1000, I assume you mean physical paper.  At a place like Staples, you could get it printed, then either spiral- or comb-bound for not very much at all, maybe $1 or less per copy.  Or maybe stapled in the middle like a school play program.

If you wanted something stich-bound with a hardcover on quality paper, vanity printing houses can deliver that.  Search on Google and you'll see many.  They have these machines like giant copiers that can take your pdf file and print and output such a book in low volumes with no manual intervention.  I suggest you be absolutely sure you have 1000 people who will want it, or will buy it, though.  Consider that many authors do virtual books on Amazon for like 99 cents, and still don't move that kind of volume.

Im not sure but I suspect it would still cost a lot. These services aren't cheap and the people that own the expensive equipment to do it will not be cheap. Try to find estimates online or contact a publisher