You can possibly find some statistical correlation between volume and price on gox, but the idea that billions of USD has to flow into gox to raise the price to a certain level, is irrational.
Here is the formula for USD flow: Inflow - outflow = increase in USD on gox. Basically, inflow is always the same as outflow, modified for change of balance.
What really moves the price, is a change of heart on part of the actors, the gox customers and potential customers. The order book reflects the value scales of the actors somewhat, but remember there are always opinions like "I will sell some at 1000" that is not in the order book.
So, when we have a really slow day (or any time interval), it means that the actors are content with their holdings. When the value scales of some of the actors change, we have trades. For instance, if someone with an order for 100 BTC at 120, waiting for a dip, changes his mind and now values BTC at 300, he will change his order and buy at the current price, driving last price up. But, equally, when someone selling for just above the current price changes his mind likewise, he will withdraw his sell order, indirectly moving the price up for the next buyer. If all actors revalue bitcoin up 10 dollars, the price will move that amount without much trade going on.
Anyway, this is not bitcoin magic, it is the same for all markets.
That isnt whats happening. Your explanation here only works if the price moved on no volume. No, the price does not move on no volume. It moves on very high volume.
It does, however, freely move thru low depth areas on low volume, for obvious reasons. The price cannot drop to 140 without someone saying,
-I want to withdraw
-I want to buy back lower [&think an opportunity is coming]
-?[Other?]
People dont suddenly agree to remove all bids leading to 140, followed by all asks dropping $3.
Yes, walls do move. And they can reduce the volume required to move the price. But again, that isnt happening now. And it is rarely a major part of price movements.