Would love to see a photo of it but it sounds like a nice piece for sure!! The new ones run an average of $600 but I would take a wild stab and guess around $800. Old models can be the preferred model! Stainless are a tad higher also. Still need a photo.
The Original Vaquero is not an "old model" so it doesn't demand a three screw premium. I might be wrong, but I don't think they were making a bisley frame for the original Vaquero as a standard offering. So whether or not it is seen as a limited or "custom" model, would have an effect on value.
The original Vaquero was bulky enough that it had little advantage over just carrying the BH which was a better sight option. It was attractive to those that wanted a cowboy gun at an affordable price, but it didn't have the handiness of a colt. I don't think it would have lasted as long as it did if it were not for all the cowboy shooting groups.
The New Vaquero is somewhat slimmer and an affordable competitor with the colt single action. It should do better.
I haven't seen where the original Vaqueros are going for any more than the usual 450-550 of the other Ruger single actions. They often ask 650 for a SBH, but you don't see them move at that price. That's just too close to new. Being .44 and Bisley, I would expect something comparable in price to a SBH.
If you work at a LGS in your own area, why would you ask a bunch of people scattered around the country what they think a gun they have never seen is worth?
You should have been your own expert in this case. I'm surprised the owner let you make a private sale in his shop. It must have been quite a specimen, or at least the purchaser thought so. I look at a lot of Ruger's, I think you did quite well on that sale.