I sort of have in my mind things that I would like to acquire and I generally purchase the item I want the most. However, I think you also have to be aware of potential changes and considering what may not be available in the future.
For instance I really want a higher end 1911, but also would like a new AR15. My finances would not allow me to purchase both, and although I really would have preferred the 1911 I went for the AR15. While some might call this panic buying I have no doubt that at least for the near future these items will be more difficult to find and more expensive.
A major source of objection to a free economy is precisely that it ... gives people what they want instead of what a particular group thinks they ought to want. Underlying most arguments against the free market is a lack of belief in freedom itself.
- Milton Friedman