For one T3 stone foundation you need 15 hardened bricks, which are 150 stone and a crafting time of 6:15 minutes in total. Add 4 shaped wood (thats 40 wood with 40 seconds crafting time). Steel reinforcements are used the same amount for both BI and T3 stone.
For one T3 black ice foundation you need 15 black ice and 6 insulated wood, which has a total crafting time of 240 seconds.
So in total you need 8:15 minutes for a T3 stone foundation vs 4 minutes for a black ice foundation (without the craft time needed for steel reinforcements, since the same amount is used for both).
8:15 is obviously a higher number than 4:00
Add this up if you need at least 5000 foundation for a decent PvP base (dagons embrace/watchers).