Didn't want to keep filling up Che's topic, sorry about that by the way. So here is my explanation of what I mean by deciding who the money is more valuable to.
There are several factors when deciding to donate or not:
Perks
Personal connection
Financial status of yourself and what you are donating to
There are many rich people who donate money to causes they have little or no connection to. While you can argue they get a perk in public opinion we can assume that at least some do it out of good will. Some no doubt have personal connections, say with people who lose a family member to cancer donating to cancer research. These aside it leaves this logic:
The rich person has more money than they can practically do anything meaningful with on their own, thus the money has more value to the charity than to the individual donating. It is better than blowing it on drugs, cars, women or whatever else.
Those of us who aren't mega wealthy have to consider the other factors more too. Playing a game gives you a personal connection, the more you enjoy it the stronger the connection. Games often offer perks for donating.
I didn't go with the expensive starter pack when donating to core exiles because that amount of money is quite valuable to me at the current moment in time. The perks didn't justify the spend, I have barely started playing so there wasn't sufficient personal connection to drop over $100. Plus with christmas coming up there are a few things I need to be spending on, not least heating as well. Thus over $100 is probably more valuable to me than to core exiles.
I did however donate $35 for an engine, since that is justifiable in terms of connection to the game - audio games cost about that anyway. It is also money I can spare, which Core Exiles can probably put to better use than I can. I can also donate again at a later point should I feel the need.
I would also rather donate the money as is than "spend" it on some in game perks I won't use. That is maybe just me though.
Hope that this explains things a little more, and that I haven't come across as stingy.
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To live by honour and to honour life, these are our greatest strengths and our best hopes.