Beheme,
Back in the late 80's, when I was in grad school, I bought a surround sound pre-amp, Carver silver nine mono amps and a CD player on credit, because I had no real income other than student loans. The interest compounded over the several years that it took to pay it off and that ended up being a much bigger purchase because of time compounding. I did it because I knew that I would eventually have the funding to pay it off but the purchase price was easily tripled before I did. There was no other way I could buy it.
One issue that no one has breeched here is the value of the satisfaction you reap from your system. It's hard for anyone to place a value on that other than yourself. If you spend several hours a day listening to music, and it relaxes you which is beneficial to your well being, then it has more value. In fact, it could end up being worth a lot more than what you are actually spending. If, however, you really don't listen very often, or it is only a "pride factor" purchase, then you are not being very wise and may well be wasting money no matter how you pay for it. I have a motorcycle that sits in my garage most of the time which is a prime example of that. I've put so much into customizing the bike that I cannot bring myself to sell it because it's not worth much more than what I've put into the mods alone now. So there she sits, a gorgeous garage queen.
The parallel about leasing a car, or purchasing anything of depreciating value other than a home, may or may not be prudent as some things are necessary for work and life in general so money has to be spent on them in some fashion and would not be strictly a luxury like audio gear. One just has to decide how much more they are willing to spend on that daily commuter (Corolla versus LS460 for example). Any dollar spent is financing against the future in that it's money not saved or invested. Only you know how much of that future value you are willing to sacrifice. The only thing buying on credit does is decrease that future value even further so you have to take that into consideration.
I realize this thread is more a survey of how people pay for their gear and you are not really asking IF you should finance an audio purchase so this, as most of the responses, are written more for those who are reading the post who are really searching for some advice about if to finance.
I've spent tens of thousands of dollars on audio gear, and I've used savings for most of it because I don't have that kind of disposable monthly cash on hand to blow on audio. If I were to order a pair of Evolution Audio MM3s, or Wilson Alexadrias, or those Wavac amps, then I'd have to finance them, which is why I don't. With exception to education, cars, and homes, I don't finance anything (unless it's zero interest).
The comment by kennyt about spending your last dollar on your deathbed is certainly an inspiring message, but of practically no real value. Unless you take your own life as you spend your last dollar, that timing is completely out of our control. Thirty years ago, planning for a ten year retirement would have been reasonable as most people didin't live much past their mid seventies. Now, with the advances in modern medicine, we are living longer even if not really healthier than generations before us. And those extra years are really very expensive when you consider the cost of that medical care alone. Thus we will require more funding for the future than we probably realize.
I try to balance my life by spending plenty along the way to enjoy life. I buy cars, motorcycles, take trips to foreign lands, send my kids to the college of their choice, etc. rather than saving every extra penny. But, I do fully fund my retirement account and tithe to my church first before anything else. But my job is very stressful and having the opportunity to sit and listen to music for an hour over a great system is theraputic, as is riding my bike on the back road with the country air invigorrating my soul. No regrets yet.