elegant: builds a system in a way that is technically satisfying
efficient: builds a system in a way that uses the least resources
effective: builds a system in way that best solves the problem
I've built a lot of elegant systems that didn't solve the right problem but sure looked good.
I've also build systems out of leftover servers and laptops that were super inexpensive.
But I've learnt that there are times where spending money is the best way to build the system that the customer actually wants (and will pay for).