I really do try not to do that. And with D&D, dice come in handy. I try to adopt the perspective of the character, but I also frequently roll behind the scenes to determine what an NPC will do (such that his behavior is not solely an extension of my will). Is there still an element of deception in playing an NPC? Yes. Is my will still behind them? Yes. But I don't (to bring this long post around) think that I do, or should do, metagaming to adjust the difficulty of challenges to match the players aptitude at overcoming them, and it is, while likely embedded in some of my decisions, a philosophy that I actively try to avoid.
Adopting an "in-game" point of view can be valuable and fun when actually playing. I don't think (as some do) that it's the be-all and end-all of roleplaying, but it's a valid and useful technique.
When writing rules or planning for a game, though, I'm convinced that it's toxic. If you design around an illusion, the illusion will tend to shatter at the most inopportune times. Rules based on such illusions are some of the most divisive, contentious and game-breaking things I have come accross in my gaming. Create illusions during play, by all means, but rules should be based on cold, hard truths (similarly to the way movies create illusions when viewed, yet still have to follow health and safety rules as they are made or risk tragedy).
I'm going to go out on a limb and say that the literal definition of the word "roleplaying" is more germane to this topic than a nebulous sentiment attributed to someone who hasn't been involved in writing D&D for decades. Not to mention, the concept of roleplaying hardly originated with D&D.
I think "roleplaying" means a gestalt of what millions of roleplayers use it to mean, not some ultra-narrow interpretation akin to method acting. As to its "literal definition" - it's possible to "play a role" in a sports team or a project team. Indeed, there are training courses that will tell you what those roles might be. For "roleplaying games", however, I'm happy for the definition to be flexible and wide ranging - which is just how it's generally used.
Sure, there are still choices that happen after the money is acquired, but if you give everyone the same amount, there's a (big) opportunity for choice not taken.
This seems to be an increasingly apparent point of division in the community, here. As best I can describe it, it's the difference between making the important choices at character creation and making them once play has begun. Since I see roleplaying games as being, primarily,
about making those choices, I am very much on the side of having the (key) decisions made once play has begun (hence make starting characters largely "equal"). But it's clear that many want a good chunk of the decisions to be made before that point.
The "give each sibling $1000" opens up the maximum range of choices
after the money is handed out. Giving choices in the money received (and the manner of its receipt) maximises the choices
before actual 'play' begins (resulting, most likely, in some players having advantages or disadvantages in play).
I can see the advantages of the former (roleplaying games are social decision making exercises, so promoting the making of decisions and having them made in a social environment is logical). Can anyone make a good pitch for the latter to me?