A number of customers have asked about whether Bricks for Bricks sells base plates. The short answer right now is no. The reason is that I have not found a way to get them at a discount price. The LEGO® Company sells the bulk of them with other retailers charging the same price or higher.
Prior to 1 Jan 2015, you could buy green and blue 10" x 10" base plates for $4.99 each from LEGO® and a larger gray base plate for $14.99. With the new year comes lots of new sets from LEGO®, but also some new pricing. The usual green 10" x 10" base plate will now be $7.99 each and there will be a tan colored 10" x 10" base plate at the same price. It looks as though the larger gray plate will remain at the same price and size. You can also buy road plates (2 per pack) for $14.99 each. Check out the LEGO® Shop at Home website for details on these.
If you're looking for base plates, I recommend you buy them straight from the source. Wait until you are placing a larger order and you can get free shipping. If you don't have a larger order coming up, let me know and I can add them to one of my orders for a small fee.