Hey Diki, good points but it leaves out the human element....especially male humans. How come so many men cheat even though they've got a perfectly 'servicable' wife at home; how come we trade our cars every two or three years, even though the current one not only meets all our needs, but has never even been in the shop, except for routine maintainence; how come we change presidents even though the current one is doing just fine (NOT referring to George W.); how come.........
So, although your arguments sound logical, ALL of us are not Mr. Spock. Sometimes we like to enter into the world of our wives, where logic counts for very little (especially in an argument). There are also other considerations.
Financial - consumerism WILL go up when it imposes no financial hardship. This facillitates the "I just want it 'cause I want it" syndrome. Again, logic not required, just money.
Improving skills - skill level has improved to the point of now being able to justify better equipment. This sometimes goes along with "this new 'thing' will make me sound better, which will translate into more gigs, which will thus help me recuperate my investment".
Also, as loyal Americans, we have a duty to keep the economy healthy by spending as much as possible, especially that portion of the economy represented by the Japanese Keyboard industry

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Finally, YOUR "truth" doesn't have to be MY "truth". There are no absolutes when it comes to human behavior. My own personal philosophy; "if you got it, spend it". For a lot of us, many of the things that used to compete for our discretionary dollars have fallen by the wayside (golf, tennis, boating, airplanes, exotic vacations, mistresses, hard partying, etc.) freeing up lots more money for more serious things, like.....the latest keyboard. Let's face it, you can't take it with you (unless you're a Republican).
chas