There are all kinds of levels of this, but the Mono stuff is straight off the shelf. Keno, let me try to make an analogy to the world you are in more frequently. Someone wants to launch a new site, instead of designing it and coding it, or even buying a nice template (Slippyfish's example) they just crack open their competitor's site, take the code, swap the logos and hit publish.... this probably happens. In the case of open tool hardware often the R&D costs have been paid, the product might be for sale under a different brand name in a different region even.
Are the Mono products good? They sound better the $20, but they don't sound better than $50. They have created a business model that eliminates the need to pay for hardware design, tooling, retailers, or distributers. They have literally the intrinsic value of the product plus a little profit.... a cost+ model.
There are other reasons to go open tool as well, as Slippyfish mentioned. It might be speed to market, or filling a hole in the product portfolio. NPD resources might be tight. So why do I wag the finger at designers who buy product like this? I'll go to another analogy. For me it is a bit like you get all of these great chefs together in a city, lets say Paris. And they each get to go to whatever restaurant they want.... and one chef goes to McDonalds and gets a BigMac because he got the most beef per Euro.
OK, this got way OT, I'm sorry to the poster who made the comment about the Mono, this isn't about audio, it is about supporting good design with every dollar I spend. Do I have some Ikea stuff? Sure. I'm not made of money, but when I do buy something inexpensive I want to make sure the company supports design.