No it in no way proves your point. In that scenario 1 set of money was made. Went from player A to player B for a sub price, then player B blew it on a house making the money leave the game. There is no economy there. That's just a massive gil sink being funded by real life money.
Please keep saying this like it's accurate. Eventually it might become real that it's safe to assume most players sit around with fortunes in their wallet and that it's safe to make broad assumptions...oh yeah even you keep saying 1% so even you know it's not a lot of people. Why should sweeping changes be made to the entire game for the 1% of people hoarding money? Them holding onto the cash literally doesn't effect anything at all. The economy moves on with out them without anyone even knowing that money is locked away. I don't even know what point you think saying 1%ers over and over again is proving. I know a player with over 300m who hasn't logged in in 6 months. That fortune is literally hurting no one. Not one person.
I have no problems with gil sinks. I have problems with you trying to offload parts of the economy onto a system supported entirely by real life money. That is not an economy. It's p2w. Even in your example the person wanted a house, used the rmt money to give a friend a free account, and then bought the house using the money get got by the trade. He purchased the house with gil yes, but he got that gil solely due to the purchasing of real money in the first place which is getting him access to something he couldn't have done otherwise obtained access to. That's flat out p2w, and on the side the player getting a free month of play was being tricked into working a sweat shop just to pay for his account off the blessings of another player instead of just enjoying the game. That's a terrible situation and is another reality to your sob story.
Real life money should never be able to create any items of appreciable and transferable worth to other players. Square already messed up badly enough by making wedding bracelets trad-able. They don't need to make it worse. Balancing the gil sinks out does nothing but make playing the game by purchasing said RMT currency a requirement from time to time. Know this square. I would quit instantly. Put that in your statistics jar.