(Replying to PARENT post)
As you said, Ryboi and Mikwaukee have the same owner, along with Ridgid [0]. They could have easily made batteries work across brands, and even added caveats to their marketing that your Milwaukee tools won't have full performance with Ryobi batteries (etc). But they didn't - because once someone buys into an ecosystem they get a strong affinity to continue buying in, rather than saving money and buying a less expensive tool that they need less. Market decommodification generally increases margins.
The main draw for the lockin, at least in my experience, is wanting a good supply of batteries to not run out in the middle of something. Whereas if I had many different color tools and one or two batteries for each color, then I'd have to be much more attentive to keeping them charged.
Personally I bought into Dewalt - the trigger on their driver felt smoother. Then Dewalt 60V - the tool I wanted had good reviews and I can use the batteries in 20V tools for longer yard work, etc. My one deviation has been the Ryobi powered PEX cincher, for which Dewalt or anybody else didn't seem to have a comparable one. I bought it as a bare tool and added a Dewalt->Ryobi battery adapter. Occasionally I'll see more Ryobi stuff at great prices and be tempted, but I ask myself if I really need it, given that it's probably "less powerful" (half marketing, half truth) and the balance would be off (due to the adapter). Meanwhile a sale on a Dewalt tool that will make my life easier feels like a no brainer, due to already having the "proper" batteries.
The main churn-gimmick I've managed to resist is buying cordless tools when corded ones suffice for the type of job. Like if I'm needing a palm sander, I'm probably working on a longer term project and it makes sense to run an extension cord, rather than needing to occasionally do a few minutes of sanding at a time. Although I admit that calculus might be different if I didn't literally have more corded power tools than I know what to do with.
[0] https://toolguyd.com/tool-brands-corporate-affiliations/
(Replying to PARENT post)
They are but I think the more official/rigorous term is "prismatic cell".
https://www.google.com/search?q=prismatic+cell
(As opposed to cylindrical like 18650 et. al.)
(Replying to PARENT post)
Most tool batteries just wrap high quality LG Chem 18650s. I don't know the wholesale price, but since they're roughly $4-$5 at retail, lets say 8x @ $3 wholesale. Then you have electronics bom/assembly (generous $10) and casing/asembly ($2) and labor ($1) for a total of $37. Following the "Double your cost and charge that rule" = $74
I made my estimate before looking up the cost of batteries, but Ryobi (Owned by TTI, same people that make Milwaukee hilariously) falls around that price point as do others. So the prices, while seemingly ginormous, aren't as absurd as one thinks. 18650 LiOn prices are insane.
DeWalt (Owned by Stanley Black & Decker) is now creating tool batteries that use flat cells (called "Pouch Batteries"), which honestly, makes _a lot_ more sense. Square tool batteries = square batteries = more mAh per unit volume. No idea why don't use these in BE-EVs.