I also think it's a bit high. You didn't mention whether it's blued or stainless. Stainless will command a higher price. Check the bore real close. As far as the white grips, look up pistol grips and you will see all kinds of them, plastic, bone, mamouth teeth, all kinds. You can bet that it's not ivory as that might be illegal. Grips can run from approx. $65.00 and up. There are a boat load full of grips on E-Bay.
They have a boat load of grips because gun owners evidently take the grips off and throw them into the boat before they throw the guns into the drink.
You might check out gunbroker to see what those guns are going for. Look at ended ads to see what they sold for.
I like the original Vaquero best, mostly cause of it's BH heavy frame and larger cylinder walls. But, I do like the way the New Vaquero handles and balances more like the Colt SAA. I think down the road, the original heavy frame Original Vaqueros will demand a bit more of a premium over the New Vaqueros as they are becoming more scarce to find as time passes... With that said, if the Vaquero is mint, $ 699 is not a unreasonable price as it's a fine sixshooter and built like a tank.