I thought this was incredibly well said, so I'm putting it here:
PANGES said:

In my opinion, an audiophile is anyone who can appreciate sound quality. Isn't that really why we're here in the first place? To find headphones that have the particular sound quality that best suits our tastes?
By definition, the word audiophile: audio refers to sound and phile refers to love or being passionate for. So if you're an audiophile, you should just love sound or appreciate good sound quality. 
I personally don't think it matters what you have or how much you spend on stuff. As long as you seek to educate yourself and find the best equipment that suits YOU, I think that's what makes one an audiophile. 
For instance, if someone is a "Car Enthusiast," you could be just driving a Honda Civic and love it to death- modifying it to fit you and your needs the best. You don't need to buy a Ferrari to be a car enthusiast. Hell, most of the people that buy Ferrari's just want it as a status symbol, and not because they love cars, thus them not even being true enthusiasts.
In essence, whomever desires and makes an effort to find the best that they can comfortably afford (or uncomfortably afford) that suits what they need/want, can be considered a "____phile" or "________ enthusiast."  
I find it funny when people come onto Head-Fi and make a thread starting with something like "Hi guys, I'm new here and I'm not quite an audiophile, but I want the best headphones I can get for $300 that is good for rock and classical." I'm sure you've all seen threads like that- they come up nearly every day. The ironic thing is, in my opinion- them even coming on here, spending time, and making an effort to research and find a headphone with better sound quality already makes them an audiophile.