If one bar would work for two months for one person, I would need to buy six bars per year for myself. My bar cost $16 per bar, so would cost $96 per year for one person. For Julia + I that would be $192 spent on shampoo per year. Another concern with this bar is that reviewers say it melts quicker in warmer months.
The bulk jug of shampoo that I was using cost $45 and lasted a year with three of us using it. That means that one year's worth of shampoo for one person cost $15 (versus $96 for bars).
As far as waste goes, the shampoo in the jug is made in the USA. It ships in a cardboard box that I can reuse + can eventually be recycled. The jug itself gets recycled + is part of buying shampoo in bulk in a store as well. The shampoo bar was made in New Zealand. It came (from within the USA) in a paper box in a big plastic bubble wrap envelope. (The conditioner bar I ordered at the same time came in a second plastic bubble wrap envelope....ugh!) I could order a year's worth of shampoo bars all at once to cut down on the number of envelopes used, but that would be a large expense all at once. The envelope can be reused, but will eventually become waste.
I'm glad that I did this experiment. It is somehow satisfying to know that I found a shampoo bar that works for my hair. Neither of these shampoo options is perfectly zero-waste, but my simple budget tells me which choice makes more sense for me (the jug). Sometimes it is worth it to pay more for a zero-waste option + sometimes it just doesn't make sense in my simple budget.