I guess the rarity could be as high as 9 out of 10. That means around 12-15 known copies. Only 4 copies have ever appeared on eBay, which is not many. And the Legend factor would have to be 9, being one of the best tracks on Flashbacks #3, and then getting it's own Norton 45 reissue.
If you feed those ratings (S8/S2/R9/L9) into the G45 Oracle, you get the following $ values
m- = $2411
vg+ = $1785
vg = $1214
vg- = $695
g+ = $447
The actual values achieved in the eBay results were
$2550 (ex condition, 2019)
$2000 (m- condition, 2011)
$1518 (vg+ condition, 2015),
$1500 (vg++ condition, 2008)
Phillydog's copy looks like it might be vg or vg- (hard to tell from the photo), so maybe worth $1000 if it's in the middle of that range