AH prices are not reflecting a shortage. AH prices are reflecting hoarding. If people choose to keep something instead of selling it, it will go up in price. The Black Lotus is not supposed to grow like apple on trees, you know that right? It's a game design choice. It's an item that is currently being hoarded - not sold. Yet still, you can buy it on the AH if your guild is bad. Because there will always be someone that is forced to fire sale something.
If you didn't plan ahead, then wait until the AQ hype is over and for the prices to fall when people realise they have hoarded too much and people stop hoarding and start selling them again.
Even if there would be more Black Lotus spawns, the price would be the same on the AH, because people simply aren't selling them to the public. Guilds are hoarding.