Hard to tell, but I can tell you this... In the Sixties I bought my first Python for a small fortune: $150. My next Python I got at a steal in the Eighties for: $416. Both of these were 4" Royal Blue wooden grips. Then I bought my first stainless steel Python, a Satin finish w/4" barrel with original Colt black neoprene grips about two years ago for $900. Last year I paid nearly $1,200. for a 'like new never fired' Colt Python Royal Blue original wood grips 6" barrel. This year I saw for sale a 'like new' Colt Python Satin Stainless steel 6" barrel black Colt neoprene grips for: $1,500. I had to pass on this beauty!
So it appears that they're doing nothing but going up in value as they are no longer made. However, consider that the buying power of the dollar is also declining. For example, in the late Twenties and early Thirties you could buy a fine gentleman's suit for twenty US dollars in gold (a $20.00 US Double Eagle gold coin). You still can buy a fine gentleman's suit for twenty dollars provided that you pay for it with the same Double Eagle gold coin. So you see, the dollar only represents value. Gold IS value.
If I were you I'd just keep that Python. I still regret having parted with my first two Pythons and I'm kicking myself for not buying that last one!
Hope that helped.
ADDENDUM: My first two Pythons were brand new. The last two were (of course) used, but in like-new conditions. There are stainless steel Pythons that are NOT the later Elite models and the less common ones are the Satin Stainless Steel. These are NOT 'Elite' Pythons but earlier models. Shiny stainless is hard to tell from factory nickel finish but any Python that has not been damaged, worn out, or re-finished is apt to appreciate in value. This also applies to the newer 'Elite' model. The rarest Pythons are the 3" barrel, 5" barrel and 8" target model Pythons chambered in .38 Special only, rather than .357 Magnum/.38 Special. If I ever 'win the lotto' I'll probably become a big Colt Python collector!
H