When I started mixing by weight, I purchased those 3-ml disposable pipettes from an online DIY supplier who sold them in 5-packs for $1.10. Then I discovered you can buy those pipettes from Amazon for $2.98 for 100, $6.18 for 200, or $7.78 for 300 - with free shipping.
http://www.amazon.com/gp/product/B005IQTSE0?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s00