Treehaus wood castle blocks 75 pcs on clearance for $11 + tax at local JC Penney store in Cupertino, CA. Website still sells them for $20 original price. Link
Now if you use JC Penney gift cards that you buy at 25% off (available at Cardpool), your price per set is $8.25.
These blocks are exactly the same wood castle blocks sold under Discovery Kids brand. Both brands even use the image of the kid playing with the blocks on the packaging box. The only difference is you get only 69 pcs if you buy the Discovery Kids brand blocks. Groupon offered these blocks (Discovery Kids brand) back in April for $19 plus $4 shipping (What a ripoff!)
If your local JC Penney doesn't carry these blocks, you can also get them at your local Bed Bath & Beyond for $15 ($20 - $5 off $15 purchase or more coupon) or $16 ($20 - 20% coupon).