First, Thank you for the Welcome and Thanks in advance for all your help. I own a construction business and currently I am running volumetric concrete trucks (mix-on-site/plant on wheels). This is the scenario:
We consumed Sand A at a cost of $21 per Ton and recently we switched to Sand B at a cost of $18.77 per Ton. However, my workers began to notice that the same 26 Ton truck was bringing less of Sand B than he used to of Sand A. I weighed both sand types in a 16oz cup and noted that there was a difference indeed. The 16oz cup of Sand A, weighed 683.6 grams while the same 16oz of Sand B, weighed 717.6 grams. If Sand A costs $21 per Ton and Sand B costs $18.77, but Sand B weighs more, am I saving money by using Sand A or Sand B? What if Sand A costs $19 per Ton?

If you want mathematical solution, take them to geotech lab, have the engineers figure it out for you. Invest by paying consultants. People don't go to school for nothing.

If you want it free, use your own common sense. If you lose money with Sand B, than Sand A is better, or otherwise.

You have about a 10% difference in price with a 5% difference in volume.

Did you weight the samples with zero per cent moisture?
That is, were they completely dry?

If not, you may be paying for water instead of sand.
Do you have the optimum moisture/density charts for the different sands?
The best way to answer the economics is to determine how you are being compensated for your costs. Are you being paid by the volume you produce or by the strength of the material placed? Which requires the most labor to manipulate?

Just from the info given it appears that:
Sand A is less dense than Sand B (volumes differ);
Sand A probably has more fractured faces that Sand B (greather strength);
Sand B is smoother & finer than Sand A (easier to work).

There are many factors that make the use of a more expensive material more profit in the end.
Cheaper materials often do not mean more bottom line dollars.
That doesn't answer your question or help much.

Could you elaborate and give some additional data about the moisture content, & how the sand is used in the final product (volume/strength)?

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Thanks Guys... I figured it out! I think my problem was that I was trying to do a weight to volume conversion. Both samples were weighed with moisture because that is how I am paying for. The outcome or end product is 1350 lbs of sand per yard of concrete. I was offered the sand A at $19 per ton so I figured:
Sand A = $19/Ton = $0.0095/lb.
Sand B = $18.77/Ton = $0.0093/lb.
16oz of A = 683.6g/16 = 42.725g
16oz of B = 717.6g = 44.85g
1 gram = 0.00220462262lbs.
1oz of A = 0.09419
1oz of B = 0.09888
So, filling my truck with 26 Tons of A means I get 552,060 ounces and with B I get 525,910 ounces. 1 fluid oz = 0.0078 US gallons, so I am getting 4312.97 gallons of A versus 4108.67 of B. B is heavier and more dense. The problem is, I buy based on weight and sell it based on cubic yard. The difference between the two is 26,150 oz less with sand B which is approximately 1.3 Tons less. So, at $19 per ton sand A is a better buy. Now, if sand A was still at $21 per ton, then sand B would be a better buy.
Thanks for all your help!

Thank you so much for your reply, it's folks like you that make the world the way it is. Much appreciated, but I figured it out!