did bitcoin prices influence the price bitcointalk account?
i only ever read from an old thread and compare the current price, and differences price is quite striking
Since the bitcoin price is on down trending , I think it will affect into account's prize
If we can buy accounts , is it possible for me to buy a legndry member?
It would be awesome to have good respect

It's possible but I've only ever seen a couple sold and for quite a lot (around 2btc). I'd recommend just putting in the effort to achieve that rank over time instead.
I would never invest 450$ to buy a account , that is totally crazy.
I think i will wait 1-2 years to get legendary and sell mine
I think you need more effort to do it. For example : your account will worth much higher if you're in default trust or green trust