If you're not prepared for these price spikes you're going to lose either potential profit from not being able to craft and sell or you're going to sell with a much smaller profit margin. So what can we do to get a little bit close to a Goblin's utopia, reaching our maximum profit every day?
Before I'm even going to mention any other options it's important to realize how the market works in WoW. Disregarding the presence of farmers (the evil kind) for now, a typical farmable item like Obsidium Ore will have significantly lower prices during the weekends. Many casual gamers will do less Auction House related activities during the week compared to the weekends, resulting in higher volumes of items sold but generally at lower prices.
Farmers (again the evil kind) mess up this pattern. Whenever a couple of farmers hit a server and reduce prices to rediculously low levels the motivation for regular farmers (the good kind) will drop. If the farmers leave after a couple of days, it takes a while before regular farmers have noticed they're gone and prices, and thus their profit, are back to normal. Occassionally this leads to prices as shown below where farmers reduced the price well below average (90g-100g), disappeared for a while and came back for another price reduction.
|Obsidium Ore prices|
Doing a little bit of research and not being afraid to invest several thousands of gold will eventually pay off.
The second option is of course to include other materials in your daily gold making cycle. Increased prices for Obsidium or Elementium Ore do not mean leathers and herbs are expensive as well. In fact there's a good chance the farmers (the evil kind) aren't gone but have simply moved to another material. Following their activities and buying when they're selling is an excellent strategy to buy low and sell normal / high.
In order to properly diversify the markets you're currently active in it's important to realize which tradeskills each resource is being used in.