Buying Borax in Bulk

I recently started making our liquid laundry detergent and I think it's great. I have been using the recipe found on the Simple Green Living site. 
The one ingrediant that has been bugging me is the borax, reason being I could only find these little 100g containers in the shops and the recipe calls for just over one of them. They usually cost R10.49 for the 100g tub.

100g Borax tub

The recipe is still very economical and much cheaper than normal washing powder, but I just had to find a supplier who sold borax in larger quantities. So after looking on the web for a little while I came across an advert that led me to Kathy from KCshop, an online store that sell soap making supplies. She didn't have the borax on the site but after emailing her she said she could supply it.
So I ordered 5kg from her on Saturday, which she posted on Monday and arrived here today (Friday). Excellent service if you ask me.

5kg Borax

And the big question is the price. She charges R35 per kg or R30 per kg if you buy 5kg! Factoring in the shipping cost, it would come to about R40 per kg. So one of those little tubs now cost me R4.
This will bring my laundry detergent price right down, not to mention how many other uses borax has in home cleaning products.

Kathy also happened to stock liquid castile soap which I have been searching everywhere for, another product with many uses around the home. I was particularly looking for it to make a multipurpose cleaning spray which I will write about as soon as I have made and tried it out.

Liquid Castile Soap