I’m looking at a catalog of things that I can have my company’s logo put on, and just a page apart I see chambray shirts and denim shirts: the chambray shirts are a little more expensive, but the “medium indigo” color looks very similar to the denim shirt (the item descriptions seem similar, too).
So, what’s the diff? What is chambray, anyway? Is it worth the extra $$?
It’s a softer weave, not quite as durable as denim, but much more comfortable. I have a couple of chambray shirts that are in good shape after twenty years of wear, and extremely comfotable to wear. The fact that both fabrics are often/usually dyed indigo (though chambray is generally a lighter shade than denim), and both are “work clothes” in origin, is probably the reason that they are easily confused.
Hmm, softer and more comfortable sounds worth an extra $8 to me. 
Thanks, Polycarp!