Not so fast. The TRICC trial published in 1999 demonstrated that at least in critically ill patients, using a lower as compared to a higher transfusion threshold led to a statistically insignificant trend towards improved outcomes in the lower threshold group. That is, less blood is better. For every reason you can think of that transfusion can improve physiological parameters or outcomes, there is a counterargument about how transfusions can wreak havoc on homeostasis and the immune system (see :Marik_2008_CCM, and others.)
Not to mention the cost. My time honored estimate of the cost of one unit of PRBCs was about $400. It may indeed be three times higher. That's right, $1200 per unit transfused, and for reasons of parity or some other nonsense, in clinical practice they're usually transfused in "twos". Yep, $2400 a pair. (Even though Samaritans donate for free, the cost of processing, testing, storage, transportation, etc. drive up the price.) What value do we get for this expense?