I did the same research last year and got pretty good feedback from Francois and Company (http://www.francoisandco.com/). I liked their french oak and was able to negotiate the flooring price down to $13/sqft (Le Bec, Le Chatel, and Turenne). Since this was still over our $10/sqft budget they proposed Montmartre ($13), Orangerie ($10), Lutece ($10). They send me samples promptly and followed up by both phone and email. I haven't ordered from there yet. I like their french oak collection.

Potentially Riverhead Building supply - heritage flooring (http://www.rbscorp.com/products/flooring.aspx) has competitive select and non select white oak that come in comparison for about $8sqft, they cut their own planks and can make them as wide as you want, but they will likely charge premium over 5-6". They compete directly with Carlisle wide plank flooring which are more expensive(http://www.wideplankflooring.com/) but their tobacco leaf stain on wide plank is amazing.

Good luck

Thank you radoncdoc! I'm off to research these. :)

Try Elmwood Reclaimed Timber. The have beautiful products. They were more than helpful sending samples and info to me a little more than a year ago.

Here is a link that might be useful: Elmwood Reclaimed Timber

We got our antique reclaimed wide-plank floor from Country Plank (see link below), and it was very reasonable. I think we paid ~ $7/sf. Customer service was excellent. I also looked at Elmwood, but we got a better deal at Country Plank.

I got the antique yellow pine, which may end up having more of an orange tone than you want, but they do have other species as well. I think for under $10, you're going to be looking at some kind of pine or maybe oak.

Here are some pics of mine just after install and sanding, after staining with a cherry stain, and then another one taken a few years later to show how it's aged.

Here is a link that might be useful: CountryPlank wide-plank flooring

redheadeddaughter- Not sure where you are, but we are in Arkansas and we are planning on locally milled 8 in. southern yellow pine planks for $1.80 sq /ft. Of course, that's unfinished and uninstalled. But, you might check some local lumber mills, especially if you're in the south.
jenswrens- Your pine floors are gorgeous! We are planning on doing new 8 in. pine planks. I can only hope they turn out as lovely as yours. What type of finish did you put on them? Just stain? What brand/color? We were thinking tung oil too, but not sure yet.