I'd say the .com (Parked) would be Low xx,xxx - Mid xx,xxx.
As the .net I'd put the value around $5,000 (end User).
If it was singular you could easily double these numbers.
Photography is still huge and probably always will be. Adding an i gives instant brandablity with the keyword. It's too bad it's not iPhoto.
If you don't plan on developing here is what you'd need to get an end user type of price.
Someone big buys/Develops iphoto.com (Not resolving)
They then buy .iphoto.net - Maybe (Resolves to blank page)
Business goes well and they realize they are losing traffic to the plurals.
They buy iPhotos.com for $45,000
They offer you 5k for iphotos.net and you counter with 10k.
You sell iPhotos.net for $7500
Now this is hypothetical, but as you see a lot would need to happen for you to get a good end user price.
In the meantime, do what the other 3 are not. Develop. Even if you make a small investment and sell royalty free images, thats a start. Personally I like those user submitted rolalty free site. Then everyone in the world practically can add unique content to your site.
Is the name good enough to build on? Sure! It's not Boardwalk or Park place, but you have a solid Marvins Gardens. Put up a Hotel and see if anyone lands on it. If anything you'll get the money you spent on the hotel, plus a little extra.
Best of luck!
Ben