As with ANY type of collectible market, the oddities or unusual low quantity type items bring the most money. This falls right in place with Quality. Always invest in the best.
The Python 6 incher is clearly the gun you will find the most of as the rest of the guys pointed out.
The 8 inchers were never top sellers for Colt.
Look at the 8 inch .38 Target Python. They could not even sell them when they came out. That's why Colt didn't produce them in large quantity. Up until about 6 months ago, you could still buy them cheaper than any other Python, condition for condition. Not any longer.
Now, the people that know Colt is not making double action revolvers are gobbling up all that stuff.
Some of the guns that were selling poorly are now bringing better money based on being harder to find.
Look at the damn 3 inch combat Python that just sold for almost $4,000.
Look at the Blue King Cobra NIB that brought over $1,300. That's unheard of 6 months ago.
Look at the Magnum Carry that just sold for $2050.
The 4 inch Anaconda in 45LC that just sold for $2125.
The standard finish Stainless 2.5 inch python that just sold for $1600.
What I'm saying is, up until a few months ago, I would have said the 6 incher would have sold easier than the 8. Now it's up for grabs and I may lean toward the 8 inch tube, just based on it being nowhere as common as the 6.
If people are trying to fill a gap in the collection, most collectors already have a 6 inch Python or 2 or 3 or 4. They probably don't have an 8.
I hope some of this makes sense.
It's a hot market on DA colts that's for sure.
Only time will tell.
Good luck out there.