Let me clarify a few things as both a healthcare professional and a regular plasma donor...
First, plasma that is donated at a plasmapheresis center (like BioLife) is NOT used directly on humans. This plasma is sold to pharmaceutical companies who use it to manufacture life-saving medications. Since human plasma cannot be synthetically produced, drug companies rely completely on human donors so they can formulate the medications. In addition, certain plasma-derived medications (IgIb, for example) can require over 5,000 units of plasma to produce a single dose. This is why those medications are so costly. My mother needed the IgIb injection and it was $25,000 per dose. These two reasons (low supply, significant demand) require that drug companies offer an attractive compensation for donors. The plasma procured at donation centers is NOT for human injection. It is used for the manufacturing of pharmaceuticals.
Second, patients who need blood products such as packed red blood cells (PRBCs), fresh frozen plasma (FFP) and platelets receive such products from blood banks. These products are derived from a single donor who's blood is divided out into the three parts which can then be provided to more than one recipient. This is the blood that is donated at blood drives and such.
I won't go into which is more beneficial or altruistic. Quite frankly, there is a significant and legitimate need for both whole blood and plasma donors. For me personally, I donate plasma because when I do, they are only taking my plasma which is mostly water. It is very easy for me to replace it, or even pre-hydrate. On the other hand, donating whole blood results in a loss of red blood cells which take longer to regenerate. I have donated whole blood before and I was fatigued and winded for several days afterward. Not everyone will experience this and some people may also have adverse effects from donating just plasma.
There is nothing wrong with using money from plasma donations to fund a Disney trip. My husband and I both donate regularly and any money we earn is our "fun money". It is money that we literally gave a part of ourselves for so we do not use it for necessities. We use it for leisure activities or "toys" or basically whatever we want. We each earn about $200 a month, sometimes less, but we do not depend on it for our daily needs. In fact, I use mine for "upgrades" at Disney. We may add a TS meal, take a tour or see a show...things that I wouldn't include in our basic budget.
Frankly, it doesn't matter why anyone donates plasma, or what they use the money for, nor is it anyone's business.