Many cheap headlights run on 3aaa batteries. You might get up to 500 lumens+, but it'll be mere seconds before the light dims down significantly. Some cheap ones might be in the 100-300 lumen range and you might get a useful amount of time on high for some tasks before the light dims down. If that's good enough for you, you can stay with what works. However, alkaline batteries frequently leak so you might have to buy a new light when they ruin it. Alkalines also don't work well in the cold or in high drain devices, so you may spend a lot more on batteries if you need the light on bright settings or work in the cold. Cheap headlights also tend to go cheap on waterproofing, yet still advertise that they are even if only rated at IPX4. You want IPX7 or 8. Basically, a cheap light will dim when you need it bright, work lousy in the cold, break when dropped, and fail in the rain. What you get from a good light is reliability. A good 18650 li-ion powered light will last several times longer than 3aaas, be regulated so it stays bright, also work with 2 123A lithium batteries for using in the cold, be very waterproof, be metal for good heatsinking and durability, and could have built-in charging, temperature regulation so it can't overheat, built-in battery tester, and reverse polarity protection (so you don't ruin the light if you put the batteries in backwards). Contacts may be made from better materials and may even be gold plated so they don't corrode over time. A good headlight can be found for $50-$100. Some as low as $30 (Acebeam H40, Nitecore NU20), depending on your needs. I like the Nitecore HC60 v.2 ($65). Spend much more and you get a headlight that will go up to over 1500 lumens for seconds (not very useful for hands free use, but useful for routefinding and signaling). A handheld flashlight is better suited for uses at very high brightness levels.
