I've actually done some research on this, and the only things I've found even close to "studies" were put out by the bulb manufactuers themselves. I've used cheap bulbs, and expensive bulbs and haven't really noticed a difference. In general if I can afford it I will buy the expensive hortilux bulb. $100 vs $40 over the course of 9 months seems like a negligible difference to me just in case it might work better. However, I've been vegging under some 1000w MH bulbs I got for $15 each from a friend of a friend light wholesaler. They seem to be doing the job, the only issue I have is that they are so cheap they don't hint at the light temperature.
For Veg I have a hortilux bulb that I paid about $75 for, but it is like 5000K or something. I beleive thats the broad spectrum that is used in regular lighting fixtures of this size, so it is more readily available. That would be the same light spectrum as even a cheap MH. I've only been able to find the 6500K bulbs (more blue) at high prices from specific high end manufacturers. It wasn't until I already had a surplus of MH bulbs around that I learned about this difference, so I've never had a 6500k temp bulb to play with to even see if I notice a difference. Had I planned in advance and had the money at the time, I probably would have ponied up the $150 for this premium color bulb by hortilux.
I guess it comes down to preference. I am sure you can find studies as to which light temperature/light spectrum is better for each phase of growing, and I would pay attention to that at least. And pick a manufacturer that you feel you are getting an honest representation from regarding those numbers.
To sum it up, my opinion is that the price of bulbs over the course of their life is pretty small compared to other things you have to spend money on. So I try to buy the best most popular that have been tested and proven over many grows. I don't think there is any chance that will hurt me, however a lesser quality bulb might, and I would never know what I might be missing.
On a side note, I do have the $75 hortilux MH bulb in 1 room, and the $15 no name brand in another, both supposedly with the same light spectrum, could be psychological, but I swear the hortilux does better. If there was any circumstance that would be testable, that is about the widest quality spectrum you could have on what is supposed to be the exact same type of bulb. I guess my point here would be, the differences are definitely not concrete in a way I could decisively say one is for sure better, so maybe it comes down to what you really want to pay for the "X factor."
