I'd say it entirely depends on your definition of "affordable." I think one of THE best items, for its current worth and pose count would have to be Gogh Reed. Granted it's a bit dated now, but it still has a very nice variety of poses- several eyes, a few wigs, animal companions and all in a rainbow of colors too (pun was not intended).
That's the first item that comes to mind, really.
Gogh reed and Zodiacal, and to an extent, Seracila pendant. I like these items because they have such a variety of items that would suit many different avatars, they're so versatile!
almost everything i can use as an "I Am" is a pose of a relatively cheap item, mostly from RIGs.
Almost all the avatars i make i use a pose of Dander and a pose of Longcat to eliminate myself from the box. From there, there's a limited number of things that show at all, almost everything that does is from items that have at least 4 poses; around 30% have over 10. In fact, the only single-pose items that work are backgrounds, and the Alchemized wings. (only the right wing for most of them, which is why it doesn't matter that they are exceptions to "relatively cheap"wink