I recall the mid-70's when one could buy 750 and 101 Spiders for $500 - $1,500, depending upon condition. Very nice, low mileage, all-original, regularly driven 101 Giulia Spiders almost never got above about $2,000. At the same time, similar condition Sprints were around $300 to $500. I never saw a Sprint bring as much as $1,000. Note that I bought a 65 Sprint GT "Stepnose" in 1974 for $500 with about 35,000 miles on it in very nice shape.
Look at the relative value of the 750/101 Sprints and early Stepnose Sprint GT's now.
Perhaps the 2600 Sprints will find their day eventually? They strike me as being better built than the Touring Spiders, although the same rust issues threaten the species.
As for me, I like having the FNM 2300 in my 102/2000 Spider. Same horsepower as the 2600, but much less weight in the front. I reckon a good 2000 Sprint could benefit equally - although as noted they really are "Grand Touring" cars, not Sports Cars.