$150 is chump change compared to $4/month? If I only spent $4/month on cigarettes, I wouldn't've seen the need to quit smoking.
To the point of the post, this is sooooo not the response I got when I asked the same question. People were all over me like white on rice on a paper plate and a glass of milk in a snowstorm. They were all like, "How DARE you question the ProVari?!?! Burn him at the stake!!!!"
Most people would read $4-500 as it was intended as $400 to $500 per month, a 2 pack a day habit here where I live with the combined taxes on a pack taking them to about $7 a pack.
I'm not a provari owner, probably never will be even though I can easily afford one, but I definitely do see the point of one, and from a technical standpoint I do believe they are likely the best power supply for an atomizer on the market today, at least that I have seen..
But I also drive a 17 year old car and own no jewelry at all, not even a watch, do not adorn myself with tattoos, and never wear anything more fancy than old jeans and a t-shirt unless someone dies or gets married. What I have is perfectly satisfactory for my vaping and keeps me off cigarettes. It's even more satisfactory than a provari -for me- because anything the provari offers to me are more than made up for by the drawbacks in its size for me. Nothing that size works with my lifestyle for portability and ease of use I require.
But I certainly won't question someone for whom it does work better for their lifestyle and needs.
Any more than I would expect them to question why I have a 1954 truck I invested 10k in rebuilding by hand, or the three motorcycles parked in my shop.

It comes down to want, not need.
Now if I were to decide to seriously start experimenting with a lot more tanks and attys, and especially if I was to decide to try to create my own and experiment with different wick materials and coil materials etc. I would then have a need for something like a provari and would likely buy one. It could happen, if I get tired of my current wants that I do not really need like working on the antique truck, the 3 bikes, and the 11 acre place I moved onto recently that has more projects lined up for me than I can complete in a few years of effort.