Buying these tools, though individually not that expensive, can add up to quite a bit of money. If you are working on only a single bike you can probably get by with minimal stuff like a set of allen keys and some lube. Everything else I'd use the co-op. If you own a few bikes, or like me, you work on other people's bikes as well, then obviously you need more.

Edit: And torque wrenches are one of the more pricey tools. I don't own one. I just ball-park it. You just have to be specially careful tightening stuff with carbon.