Offsetting cost of this hobby...microstock?

I've got stock from D70, D200 and D700. I always shot D70 at base (200), was able to go to 320 on the D200, and I've had a few 1600 ISO accepted with the D700. Funny thing is, I still make a few dollars off the old D70 pictures.

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Eric
http://www.pbase.com/cerumen