According to his video he used a 12" hemisphere but said he should have used the 14" hemisphere which is 36.90 (x2) even if you went with a 24" one it is $85.00 (x2) it is only when you go over the 24" boundary that the price jumps because of the size of the machine needed to do the larger sizes.
2 14" white hemispheres $73.80
1 string of 100 Pixels $66.36 (cheaper if bought with other items)
1 Smart String Controller $10.04(plus shipping depending on coop amounts)
Sub total $150.20
Plus figure another $30 to $40 in other materials and you have a sphere....