The economics of mining in space are hotly contested, with some estimates claiming as much as US$20 trillion worth of precious and industrial metals in a single asteroid, while others point out that any efforts to extract these materials and bring them back to Earth en masse will necessarily flood the market and cause prices to crash, potentially (or probably, or even definitively, depending on who you ask) making the whole endeavor self-defeating. Frankly, if the experts can't even agree on whether or not it could be economically feasible to mine asteroids and bring the materials back to Earth, I doubt we'll be able to give a solid answer either way.
Where space mining could come into its own, however, is in space-based industry. Currently, according to NASA, it costs US\$10,000 per pound to put anything into space. While NASA's goal is to reduce that to around \$100 per pound by 2025, they don't yet have anything that could do that, and even if they do manage that let's put it into perspective: at that lower, post-2025 cost, it would cost over \$81.6 million to put the ISS into orbit, which while an impressive feat itself is quite limited in its scale, and much too small for anything even remotely considered "industrial".
Given such high overhead, it's really no surprise then that we really are not doing a whole lot out there. But if we can bring raw materials into orbit for cheaper, then suddenly the economics of space-based industry become a lot friendlier: It's a lot cheaper to move around in space than it is to fight against gravity and escape Earth's surface. Just look at the Apollo missions: Compare how big the Saturn V rocket was that had to get the CSM/LM into space, versus how small the CSM/LM were for getting all the way out to the moon, landing on it, getting back into lunar orbit (into a retrograde orbit at that (a consequence of the free-return trajectory Apollo took out to the moon), much more costly than prograde!), and then returning to Earth. Solid numbers: 1,000 times more mass required to go 2,000Km than needed to go almost 800,000Km!
So what would we do with space-based industry? While there are a few super-high-tech things that simply work better to manufacture in micro-gravity than here on Earth, for the most part anything made in space would suffer the same self-defeating diminishing returns if we try and manufacture it for the purpose of bringing it back to Earth. That doesn't mean it won't be done -- could be a good way for some manufacturers to get a leg up on their competition -- space-based industry would most likely exist to service space, not Earth. Which means we probably won't have it until we have a need for it, i.e. we won't have space-based industry until we're doing things in space that would benefit from it (living in space stations, extra-terrestrial colonization, space tourism, etc.); the Catch-22 is that we (probably) won't be doing things in space that would benefit from space-based industry until it's economically feasible to do without space-based industry, though granted even then space-based industry would probably be cheaper than flying things up from Earth.
If you really want to bring stuff down to Earth from space, you could always build cheap, single-use "dropship"-style pods in space and literally drop them down to Earth. The cost is fighting against gravity; using it as your version of a FedEx driver is actually quite cost-effective! Just beware of the fundamental law of economics: As you increase the supply of some product/material, unless you also increase the demand by the same proportion (unlikely), prices will necessarily drop, which will of course cut into any profits you might otherwise have gained.