I have never met a developer who said they had enough time to "properly" finish their project. Sure, everyone starts the project with dreams of how this will be momentous - somehow the stepping stone to curing cancer and world hunger - but then reality sinks in and the team scrambles to make the best of their limited time.
And that's where economics, the science of how people deal with scarcity, comes in. I had to take a micro and macro Econ course back in college for my engineering degree, but back then it was just an 8:00am commitment. When I was reading Joel on Software's blog, he picked my interest with economics again with his talk of compliments and supplements, vendor lock in, the chicken & egg problem, etc... So, I got a copy of "Economics for Dummies". I saw it as Part II of The Complete MBA for Dummies.
Living up to the "Dummies" genre, it was an easy read. The concepts of utility, marginal revenue, return on investment (ROI), consumer surplus, diminishing returns, and supply and demand are good things for any developer to know. Much of this may seem like common sense in today's world, but a book helps one to articulate what their head thinks is common but they can't find the words for.
Besides assisting with prioritizing features and making calculated risks, it helps a technical person continually appreciate the business side of things.