I have every tradeskill @ 525, some I use regularly, some I barely use at all. That's OK, I am a collector of recipes (even recipes that I have no intention of ever using - BOP low level gear anyone?). One of these days I will level another couple of toons and get 3 gathering skills.
I am no Breevok with the ability or inclination to closely track sales. I find it difficult to know what actually sells well. Yes, I have Beancounter, but it still doesn't do it for me.
A very simple method that works for me is to have a stable of alts - each selling a niche. My selling alts are low level, ususally not the toon that does the original crafting.
When a selling toon wants something made (or mats stockpiled) - it is responsible for the gold for that transaction, to the nearest 'round' number.
When I follow this process, I can see at a glance which professions (or parts of professions) sell well, and which perform poorly - for my playstyle. If it does well - it has gold. If it does poorly - it runs out of gold.
The one period I didn’t do this - I got into trouble. I kept buying herbs and inks- taking gold from profitable markets, and ploughing them into glyphs (after all - this blog is 80% glyphs - I could not possibly lose money - ... oh well - maybe I could). I never became 'poor', but did manage to carry too much inventory , and to send good money after bad.
I was already well on the roads to recovery before my significant competition moved on, simply by concentrating on what was selling well, and finding alternatives to what was selling poorly. The fact that a very deep undercutter has since moved on helps.
If you only have your finger in one AH pile, it doesn't matter so much. If you play with multiple markets, or even sections within a market, it is worth segregating it with selling alts and keeping your gold separate.