If I remember correctly, you have a 125 gallon tank you're building, so you're going to need a lot of rock
I agree with the reply from Atoll, I would try to find real, wet live rock from someone's tank that's breaking down. There's some downsides to doing this, but I think the benefits of using live rock outweigh the possible negatives.
Otherwise, look for bulk dry rock, not just small packages of 5, 10, 20 pounds, which can be very expensive per pound.
Here's Nature's Sea base rock, 40 pounds for $85 from Chewy
This was the best deal on base rock I could find in a few minutes of searching. Do a little more digging, you may find even better deals.
Good luck!