I can spend a good deal of time criticizing Ikea but on one thing I can't: their furniture is incredibly easy to copy and upgrade into a better version with minimal effort.
I took the time to break down, piece by piece, in a crazy exercise of reverse engineering, a love seat, to understand how they had designed and put together the thing.
After that, I sat to run the "numbers" and realised I could make it cheaper, sturdier and add storage room to it, with minimal modifications to the basic plan.
It was very interesting to discover.