As has been said, zero chance that you can get free shipping on FLA or SLA or AGM batteries unless the purchase price is jacked up to begin with.
I assume you mean 2000Ah @ 6V since that is what GC batteries are. So that is 12kWh. Deka GC15's are 230Ah @ 6V so you would need a minimum of 9 of them. And since that is an odd number and won't work in a battery bank, lets round it up to 10. I am going to ignore your too-good-to-be-true deal you have there and take a real deal from Lowe's currently at $144 each with free pickup in store (
https://tinyurl.com/eapk4c). So that is $1440 plus at least $80 in tax unless you live in a no tax state. So lets just say $1500. But then if you want a good cycle life out of those batteries you will have to only use about 50% of their capacity so double that number to give yourself a fully usable and long-life battery bank with a final cost of around $3,000. Since the DEKA GC15's are rated for 700 cycles @ 60% DoD that is around $4.30 per cycle and that doesn't include battery terminals, interconnect cables, breakers, etc.
OR you could get a 48V Kong from BigBattery.com that is 12kWh, fully contained in its own case like a Powerwall, and costs $4,300 plus shipping. So lets say $4,600 since it ships freight. It is rated at 2,500 cycles at 100% DoD so that is $1.84 per cycle and has a 10 year warranty. Oh and it is made in California.
If I'm investing that much money it is a no brainer.
P.S. - I can get you 10% off with my affiliate code if you are interested. Hit me up on a pm.