I take of advantage of samples whenever I can as well, but you still have to consider the cost on parts in the event you want to build the project in some number. The BOMs I end up with for these projects are usualy about a page long. 50 cents or a dollar doesn't sound like much for a component, but it adds up fast for bigger parts lists. When I see chips with costs of several dollars it makes me cringe. The 10 bit digital pot I'm using for my latest project is about $5 and the converter controller is about $7, yikes! At only $3, the MCU is cheap in comparison.
The one thing that's always really cheap is SMD capacitors and resistors, but the caps get expensive when you get into the higher values. I'm really pleased I found a 22uF MLCC cap in a 3225 size that will work well for only 50 cents, but still, I have to use 3 on the output and 2 on the input for the converter. That's $2.50 in capacitors. Not cheap compared to the one or two cents a piece you usually pay for those parts. The MLCC caps are great, but the higher values can get expensive and can have issues with DC bias. If you can get around that, they have huge advantages over other types of capacitors.