It's not particularly easy making a custom headlight in the same price range as commercial ones.
There are some high-end headlamps around, but most of the ones I know of are aimed at cavers, and so are principally made for helmet mounting rather than as straight headlamps (Scurion, Stenlight, Rude Nora, El Speleo) .
There are also some modules to fit in existing lights, such as the ones for Duos that John at Customduo makes, and the ones I make, but even to make a decent insert does end up costing meaningful money in terms of parts+labour - as soon as quantities are low enough that anything is effectively handbuilt rather than factory made, that does push the price up quite a bit.
Most such things tend to be twin-beam, which for caving use does make them a heck of a lot better, but also adds to the price.