A lot of PI is very expensive compared to historical prices.
I prefer to trade mostly in 'P2' , easy to make, with good compression (not as good as P3, but certainly easier). P2 'refines' being the first of Foo's Eve PI spreadsheet - Manufacture Tab
Fuel block based PI (Coolant, oxygen, mechanical parts) have mostly depressed pricing. Enriched Enriched Uranium is ok but even that is down from it's peak. POS fuel is more expensive but that is due to the addition of strontium clathrates (now being 14% of the cost), and is not caught up in the PI demand for citadels.
Some 'P2' is crazy expensive. Microfibre shielding, Polyaramids, Silicate Glass and Test cultures are all sitting above 30k. These normally are at the 10k mark.
On that note, I have changed (again) the cache setting on my pricing spreadsheet. Possibly less stable, but definitely more up to date.
I also have been trying my hand at twitter, For someone as verbose as I can be, the 140 character limit is an interesting challenge. I have already found that there are some ideas worth expressing but not worth a full blog post.