When Huntington became the Pirate's GM he stressed investing the teams money wisely and finding undervalued commodities. This is one of the main ideas of "Moneyball" as most know by now.
He has done this a few ways. In trades and free agent signings he targeted players that he thought had upside but other teams had lost their taste for. Sometimes it has worked out well (Tabata, Ohlendorf, Jaramillo) and other times not (Craig Monroe, Vasquez) but for the most part it's too early to tell (Milledge, Clement, Morton etc). However now it seems that with the young players in the system he has begun making safe bets of 1- 3 million at a time on relievers who are average to solid, but capable of pitching very well.
While it is generally regarded as foolish to spend "big money" on relievers as their performance fluxuates greatly from year to year, it is an excellent investment of 1-3 million dollars on guys who have proven that they can be excellent relievers in the past for that same reason. You are not spending a great deal of money, and based on past performance you will probably get a decent reliever. While the guy could collapse, there is an equal if not greater chance that he will pitch better than expected. If that is the case you have gotten a great value. Aside from the addition to your team, if you find yourself out of contention around the trading deadline (cough cough) they are always in demand and can thus be used as trade chips to get young talent that you need at other positions. Having them attached to a one year contract at a reasonable rate makes them all the more appealing for good teams looking to bolster their bullpen for a post season run, rather than commit multiple years to a guy as a long term piece.
Additionally there is the affect that is has on a young rotation. It is often stressed how important it is to a young pitchers confidence and performance to have a good defense playing behind him. A great play to get a guy out of a jam goes a long way when the floodgates are about to open, as well as the negative mental impact watching balls drop or go through holes. Having a reliable bullpen to hand the ball over to is equally important to that development. When a young guy goes out and pitches a great game and leaves with the lead, he deserves to get the win and be reawrded for his work. It's not easy for a guy trying to establish himself to hold up his end of the deal for 7 innings and then watch Tyler Yates blow it.
Sure they could be just as bad as last years bullpen, but I think that spending moderate money on solid if unspectacular relievers is a great investment of the limited budget for such a young team.