If these are so cheap and easy to install from places like Home Depot, why does Ikea sell their very expensive and complex systems? Am I missing something?
Two different business models aimed at different sets of people. Ikea* makes sure their products can be assembled even by people who are uncomfortable swinging a hammer and own zero tools. Home Depot covers everything from casual DIYers to contractors building homes from scratch.
The Ikea stuff is all plug-in-play (to borrow a computer term). You could literally use velcro-tape for adhesion and a pair of scissors and be done with it. Think of it like a lamp; you plug it in and it turns on --- and it has a big markup in price ($).
Specifically regarding LED lights, the stuff sold at HD or Lowes isn't much more complicated, but you have to cut the LED tape to size and puck-lights involve drilling some screws and whatnot. It works just as well (better, IMO, because you have more control over the length), but because HD normally deals with contractors for much of its business (and thrifty DIYers) it has a more narrow profit margin, so the same absic components are cheaper. Note that this is true for the vast majority of stuff it sells vs Ikea.
Then there's the stuff sold on Amazon, often from overseas. It's super cheap because there's no middle-man, no stores, and warranty claims take a leap of faith.
