What a fun tongue-in-cheek topic,
Aina!

I think the reason Gandalf the White got a new staff was so that the weapons companies could sell two versions - Grey and White. That is certainly the reason the Witch-King broke Gandalf's staff in RotK as well - but they messed up their chances when they only got it into the EE version. So I'm not sure if the third staff was given enough screen time to be sellable...
And of course Gandalf only got new white robes so that they could sell a second version of action figures!

After all, the other characters walked around in the same grubby clothes the whole time - why couldn't he?!
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'Mercy!' cried Gandalf. 'If the giving of information is to be the cure of your inquisitiveness, I shall spend all the rest of my days in answering you. What more do you want to know?' 'The whole history of Middle-earth..
.'