Condition is everything but, for a 6" blue Colt Python in say 95%+ condition you honestly cannot lose paying $850.00 - Go to gunbroker.com & type Colt Python into the search block.
There are usually quite a few of them on there in Nickel, Stainless Steel & Blue and in various barrel lengths and degrees of condition.
Scroll through them all and click on the 6" Blue Pythons and compare the one you want with the photos and asking prices.
Keep in mind though that some GunBroker sellers always ask a premium price and their guns often do not get bids.
For a nice condition Python that has not been screwed around with you're usually safe paying any amount under a grand.
MINT condition & Vintage N.I.B. (of course) fetch much more.