This seems to be the central line of approach, in your response. So, forgive me if I ignore the extraneous matter.
Firstly, I have deliberately kept my definitions qualitative, rather than quantitative. As you have yourself previously pointed out, the cost of living varies with geography. So, clearly, no one number will do. Nevertheless, my definitions are not quite as vague as you pretend; we all know what is meant by dignity, and it does not include the necessity to beg on city streets, for example. And the condition I put in brackets, which you seem not to have noticed, that reasonable dignity should be limited to a quality of life that one could realistically wish for everyone, adds a touch of egalitarian rigour.
Once again you're talking in very vague terms while complaining about me highlighting your vague terminology. What is "reasonable dignity"? Does it mean having a roof over your head? A flatscreen TV? A spare bedroom for those overnight guests?
Clearly no one number will do regarding wealth - my point regarding geography was that figures that initially appear horrific - "X million people live on less than $3 a day" - don't paint the picture they first appear to paint. If you live in Manhatten $3 barely gets you a coffee. If you live in Sri Lanka $3 goes significantly further.
Of course there is little dignity in begging on city streets. What dignity is there, or should there be, in living on the back of another while doing nothing to support yourself? How is it dignifying to someone who is capable of working, to just be given things without having to do anything for them? What dignity is there in a social welfare system that takes away hope from people, by giving them just enough to get by and pairing it with the threat of taking it all away if they try and better their own situation through their own efforts?
Despite your objections, I think we all know also what is meant by excessive wealth, and it is wealth in excess of one's justifiable needs. These needs may indeed involve the occasional luxury indulgence, but it clearly does not include an entire lifetime of such indulgence.
Clearly there is no clear definition of "excessive wealth", especially since you yourself commented on how you did not believe you were "excessively wealthy" and as far as you were concerned that was the state of affairs regarding your life. A billionaire could say the exact same thing if they chose.
Even in this paragraph you're talking in very vague terms. An "occasional luxury indulgence" is fine but a "lifetime of such indulgence" is not? So what counts as a "luxury indulgence"? Anything not 100% essential for survival? Anything the majority might find unaffordable?
To be clear, my objection is not with an assertion that we should look after the poor among us. My objection is with universal questions about why a Christian would want something when that something is only vaguely defined and when the person asking the question appears, on the face of it, to be looking to exclude themselves from the potential implications of their question.
For example, is a computer a luxury? Of course it is, we could live without computers (as indeed we as a species did for however many thousands or millions of years before they were invented). So owning a computer in the long term is arguably a "lifetime of indulgence", while drinking an entire case of vintage Dom Perignon is arguably an "occasional luxury indulgence".
The fact that I am asking people to make judgements in respect of these matters seems to bother you, but the reality is, unless one practises arriving at moral judgements, one is never going to get any better at making them. And, in respect of wealth, in this unequal, unfair world, we surely need to.
Moral judgements are all well and good but in coming to a moral judgment we either need to let people decide for themselves, or come up with some clear-cut definitions. "Thou shalt not commit adultery", for example, doesn't leave a whole lot of wiggle room. "Christians shouldn't be rich" falls down unless it can define what "rich" means in objective terms so it's clear who is "rich" and who is "not rich".
If you want to make a moral judgment that you have more than you need then you are free to give as great a proportion of your material wealth in whatever way you see fit. If, in your eyes, you are "rich" then you are free to give it away. If you choose to pick a single street beggar and give them so much money they can live in a palace for the rest of their days that's your call. If you choose to pick a wealthy man and give him money so he can wash his Ferrari in Dom Perignon and escape the indignity of using mere water that is also your call. If you choose to give small amounts to lots of individuals, making a small difference in each of many lives you get to do that too.
Mostly, when I get on my soapbox about this issue, people object for one of two reasons. Either they are rich, and want to stay rich, or they are not rich, and want to become so. I am simply suggesting that neither of these are acceptable ambitions from an ethical (and therefore Christian) point of view, given the state of the world we jointly and severally inhabit.
The problem isn't money, the problem is when money becomes our God. There is nothing wrong with having money, as long as those who have it are willing to use it as God directs.
I'm quite happy to leave people to decide for themselves what to give, whether out of their abundance or sacrificially giving out of what little they have.
"So let each one give as he purposes in his heart, not grudgingly or of necessity; for God loves a cheerful giver."