I just saw El's new pages about Valuable Fish, and would like to start a discussion about them. I already submitted the message below as comment, but thought it might be a good idea to post it on these forums too.
Very nice guides indeed, thank you!
However, I have my doubts on the values you have put in the "median auction value" - I would like to suggest you to remove that column, or replace it by some kind of abstract 'index' that can be used to deduce the relative value of cooked fish, but not any absolute value. The reason is simple: the values of auctioned goods vary wildly over different realms, and even are different between horde and alliance AHs. Also prices are not stable, but fluctuate - possibly a lot. If there were a smallish margin around the value that would be encountered in practice, then showing real prices would make sense (after taking a median, of course). But reality is different ...
As an example of the problem, consider El's price for cooked deviate fish (savory deviate delight) - 70s in the list. On my alliance realm I sell these normally for 3g a piece, and on my horde realm at 1g50-2g. Both prices are rather far away from your "70s". reasonable prices for stacks are sometimes different depending on the stack size. Or a different example: I have been selling furious crawdads (raw) at a going rate of 4-5g a piece during the past months (the raw crawdads sold for more than the cooked ones, presumably because they can be used to level cooking to 375). In the past weeks, since the arrival of achievements, the price has crashed down to 50s-1g a piece, because many people are trying to get the crawdad pet, and get loads of crawdads as 'waste' product. The prices are not stable.
I think that listing any single price value is not going to be very helpful for these two reasons (realm differences and value evolution over time). Listed prices will be taken be many as "this is the price I should sell my stuff at", ignoring (and possibly upsetting) their realm economy.