EagleTac propitiatory battery workaround?

Does anyone know a way around this?

https://illuminationgear.com/products/eagtac-mx30l3-r-3500mah-battery-pack

They want to charge $46 for three protected 18650's. Most multi cell lights use a holster for your own 18650's.

Not buying the Eagletac lights that require this proprietary battery sounds like a great way around that. I'm of the opinion that companies who do this sort of thing should be punished.

Battery packs aren't magic. Three 18650s with pre-welded nickel tabs, some wire, some insulators, some heatshrink, protection ICs (optional, but you're charging in series here) and a brass button or two would be all it takes to replicate this. You probably won't save much money buying those components in individual quantities versus buying the premade battery pack.

While I agree that proprietary battery packs seem over the top for the enthusiasts on this forum, but it also serves a purpose for company's to avoid liability and enforce quality control for high amp application. Regular users mixing and matching batteries could have detrimental consequences if not done with care.