Yes, the number of bitcoin is increasing at an almost constant rate (for now), but not the price to produce them! Higher difficulty means the energy and effort to produce a bitcoin will be higher so miners will not sell it at a low price. Would you sell something you payed 10$ for 7$? I guess that's a no.
So if you paid $1000 for $100 worth of gold, would that make gold rise to $1000 soon so you could sell it or would it just make you stupid?
Mining bitcoins for $10 when the price is $7 will not drive the price up. This is a logically fallacy and you're conflating sunk costs into price. What you paid, you paid, you can't change that. Beyond that you will want to sell high and buy low
just like anyone else. If you think $7 is low and it will eventually go to $10, then you hold on to it. If you think $7 is a peak, then you're a fool to hold on to it even though you're selling at a loss. Miners do not dictate the market and they do not even put pressure on market prices. Supply is supply, demand is demand.
Would I sell something I paid $10 for, for $7? That question requires more information. If I bought something worth $2 for $10, and someone stupid offered me $7 for it, I'd be stupid not to sell at a loss because the whole situation is stupid all around. When mining becomes too expensive miners will stop mining, not continue paying for bitcoins in the hopes that they can sell them higher than the current market rate! (Unless they believe price to increase dramatically in the future!)
You seems having hard times understating that. Will you buy something for 10$ (keep mining) and resell it for 7$?
If the sole perpose of buying the item is to sell it, then buying for $10 and selling for $7 is silly. But people often buy items for more than they could sell them for. Consider buying a new car for $20,000. As soon as you drive it off the lot, you could maybe get $15000 for it. People buy cars all the time, are they all stupid? And now you will probably say bitcoins have no other use besides being sold, that argument has been addressed here on the forums already.
See the poll about when people will quit mining:
http://forum.bitcoin.org/index.php?topic=24542.0