A good quality neo typically goes for about 3 dollars each, irrespective of the color from what I have seen. I would agree that reds are most in demand, followed closely by blues.
If you want valuable you will have to step away from Neos and look at some of the rarer caridina morphs coming out like boas, galaxies, fishbones, etc. Or other types of shrimp like sulawesi. However I am not sure you would sell as many to make up for the difference in price compared to just trying to sell popular neo colors.
Yes, physical stores will be more expensive, I tend to only deal online for buying/selling and the sites I go to its about 3 dollars regardless of color.That varies greatly depending on location. In the almost 3 years I've been keeping fish I don't believe I've seen them in stores for less than $5.00 each, and now they're at least a dollar higher in most places. The most recent place I noticed had reds for $4.99 and blues for $5.99.
I'd like to know where you're finding shrimp at those prices, the online stores I know about have blue diamond and bloody mary neocaridinas at like $8-15 each...Yes, physical stores will be more expensive, I tend to only deal online for buying/selling and the sites I go to its about 3 dollars regardless of color.