General purpose LED bulbs seem to vary a LOT in price... from $1 per bulb to $40+ per bulb... and there doesn’t seem to be any tangible difference between them. I mean, some say they last longer, but it’s never enough to justify 10-20x the price. And the lumens per watt are pretty much the same. Am I missing something?
You're missing a lot, but you might not care. You indicated longevity is not a factor, so that takes care of one category of differences. Let's note a few other common differences between cheap and expensive LED bulbs, so that you might make an informed choice based on what's important to you:
Improvements in Expensive LEDs compared to Cheap LEDs
Efficiency: usually good bulbs are more efficient, in terms of lumens/watt. With a dramatic difference (say 55 vs 85), the saved electricity can pay for the differences in the bulb, depending on power cost and duty cycle of the product's lifetime, which as noted, also tends to be longer on higher-quality bulbs.
Heat: dirt-cheap bulbs use cheaper internal power supplies that tend to generate waste heat. Better bulbs use a fancy electrical driver known as a "switch mode power supply", which can be up to 90% efficient, compared to a resistive or capacitive dropper with as low as 50% efficiency. Heat lowers lifetime, so if your bulb will be in a globe, can, or other enclosed area, this is a factor worth considering.
Color Quality: Better bulbs tend to have both higher CRI, and less color variation within models. I've gotten two dollar-tree bulbs from the same peg, and one was about 250deg cooler than the other. I've gotten two different phillips bulbs months apart and they both have identical coloring. If you don't have a lot of bulbs going at once, this is more important than when a bad apple can hide in the bunch. There's also some health/wellness concerns about an over-concentration of blue light, and it's bio-rhythm effects, and in this regard, the more-balanced light of quality bulbs would reason to have less impact.
Light Quality: Cheaper LEDs (especially those with cheap capacitive dropper internal power supplies) tend to flicker at mains. This can be more noticeable at night, and in your peripheral vision. Prolonged exposure causes some people headaches or just distracting corner-of-the-eye rainbows or flashes. If all your bulbs are the same and they all flicker, the effect can be quite pronounced and annoying.
Performance: cheap bulbs can take longer to turn on, which is especially noticeable when one switch controls many lights. This can make a good automation system seems laggy, which nobody wants. Another performance factor is backwards compatibility with existing dimmers, dusk-to-dawn sensors, motion detectors, etc. The parasitic current of such devices often causes less sophisticated bulbs to dimly flicker when the switch is off. Better bulbs use a couple of electronics-based tricks to eliminate or reduce such an effect (sensitive gate SCRs, bleeder resistors across caps, post-DC switching, etc). Also, some cheaper drivers can create audible noise, either a hum or whistle (especially when dimmed), but I've not heard that on quality bulbs. Lastly on this point, quality bulbs last longer, so if the bulb is hard to reach, like an outdoor yard light, that could be a strong consideration.
Considering all that, you still need to consider your usage as well. Weight the factors important you you (if any) and shop armed with the knowledge to get the best deal for your needs. You don't always needs the best, and I use dirt-cheap ones in some places myself, even after noting all the above!
You can likely live with a cheaper bulb you use 2 mins a day in a closet better than you can cheap task lighting. If you don't have enclosed lamps, heat's not a big factor. If you lived happily for years with mixed CFL+tungsten lights you probably won't care about color temp differences or CRI. If you don't pay a lot for grid power, efficiency isn't as important as it is for those off-grid. If you don't have dimmers or other "fancy" switches, backwards compat doesn't matter, etc.
You be the judge. You can spend $5k or $500k and get a reliable car. Same with stereos, or anything really. How much you need depends, but now you know what to look out for...
A huge factor in LED pricing is local subsidy provided by the electric utility* or local government.
However, build quality is very important. Items sold in big-box stores and dollar-stores are very heavily "cost-shaved" to make them a few pennies cheaper (on the production side).
The problem is, if you start with a quality LED and start shaving pennies, where do you cut? The easiest place to cut costs is the electronic driver circuit which regulates power to the LED.
- Use a cheaper capacitor-based driver circuit. Unlike most electronic components, capacitors "wear out" like batteries so better LED makers avoid them. (realistically the LED emitter will outlive all of us).
- Worse, shabbily made or cheap capacitors are prone to failing much sooner.
- Fail to solve the crystallization problem in RoHS solder.
- Design a system that runs hot and fail to cool it adequately, causing failure of the electronics.
- LED emitters are manufactured and sorted into "bins" (the process is called "binning") based on their performance and light quality. The bins are sold competitively, with top tier builders bidding top dollar for the best bins. Buy from the cheap bins for worse light.
- Buy from no-name LED manufacturers who make poor or unreliable emitters.
- Use cheap plastic that deteriorates after a few years, causing the unit to fall apart
- Fail to isolate the power supply, so the metal heatsink is electrically "hot"
The upshot is that discount vendor can do you a whole lot of damage. And worse, big-box stores and dollar stores are the absolute worst at "shoving these products down your throat" to where it seems like nothing else is even sold. Three brands that have given me nothing but trouble are Utilitech, Feit Electric and Lights of America - and all three are darlings of the big-box stores.
- Go for the lower "Energy Star 2.0" standard, which allows for a much shorter certified life (as opposed to the higher "Energy Star 1.1").
So it is very much a matter of "caveat emptor". As a rule, I stick only to top brands and IKEA, which I have always had good luck with. General Electric knows a thing or two about how to make a light bulb. (they were Thomas Edison's partner in initial production of light bulbs).
* Why would the utility pay people to use less of their product? Because it costs a fortune to build a new power plant. When plants cost more than $1/watt, helping customers conserve makes sense when it can be done for less than $1/watt. The government clears the way for this with supporting legislation.