What is the value of a 1907 US 10 dollar gold piece?

In all but the top grades this coin's value is determined by the current market price of gold. Numismedia lists the following approximate retail values as of 09/2012, regardless of mint mark:

Very worn condition - $940

Moderately worn - $960

Slightly worn - $980

Almost no wear - $1,010

If the coin is uncirculated, look on the back to see if there's a small mint mark letter below the eagle. It may be blank or there may be a D or S.

No mint mark (Philadelphia):

Uncirculated - $1,150 to $5,200 depending on quality

"D" mint mark (Denver):

$1,150 to $7,490

"S" mint mark (San Francisco):

$1,250 to $1,625

DISCLAIMER: The retail values quoted are the best available as of the date shown, but may vary significantly due to changes in the precious metals market. Also the wholesale (buying) price of a coin will be less than the selling (retail) price. A reputable coin dealer will be able to give a more accurate valuation based on inspection of the coin.