Case and point my car. Had a fantastic Toyota $8000. Cost me nothing in maintenance and $150/mo car payment. Told myself I am blowing $150/mo on toys why not upgrade to a 286hp high miles Acura (115,000) and really enjoy the driving that I do do instead of puttering around. If I just waste $150 less a month I'll break exactly even. Nope. Didn't work. Cascade effect. Now that I'm psychologically in my dream car, a 'luxury' car, I feel like I need to park in the covered garage, and I feel like it is okay to go to nicer restaurants because my car looks fine in the lot surrounded by other decent cars. Tires? They don't cost 2x as much but 6x as much! Brakes are 4x as much. Car insurance skyrocketed from $36/mo to $56. Oh and I have to use premium gas. This extra $150/mo car payment is the LEAST of the additional expenses the more exciting car cost me.
Same happens when you live in an upscale neighborhood or buy a nice house...it becomes infinitely easier to justify tangential expenses. Read The Millionaire Next Door to understand this effect better.