I had a budget in mind and then went and played a few. My ability is/was limited so I bought what felt right rather than what sounded right. I have grown to love the sax I bought, and now realise I bought beyond my ability, but have grown into it. When GAS attacked and I had to get a tenor, I knew the sax I wanted, mid price, reliable name, and I went and bought it.
The real dilemma for me was am I going to use this as much as it costs, and get value for money? Once I knew that I would put a lot of time into playing, I didn't mind the expense.