@Wookie there is definitely a massive profit margin in there for companies like SS and anyone else selling DPV batteries. If they are making their own, there is a huge expense in the equipment required to do it properly and since the market for batteries is pretty small, they have to spread that across an unfortunately small number of customers. This is all going to start changing quickly though as the shipping regulations start getting tightened. I think you'll see a lot more companies going to a design similar to what Dive Xtras has done with the Piranha, or even what UW Light Dude has done with their battery packs.
UWLD has one small battery pack that they then stack in 2p or 3p for the larger canister sizes. That pack is custom to them due to size limitations and optimization for a dive light which is a bit more strict than on a scooter.
Dive Xtras is using an off-the-shelf e-bike battery for the Piranha and using the same concept as UWLD with their battery slices. If you have a Piranha and the battery dies outside of the 18 month warranty period *which is huge compared to a company like Silent Submersion that only warrants them for 30 days*, and are crafty, you can remove the pack, find out what it is, and go buy one commercially. Since it is for an e-bike, it shouldn't be that difficult. We are likely to do something similar with a Viper LiFe here shortly.
Part of the problem with doing that for other scooters is they use uncommon voltages. Most e-bikes are 36v, that won't cut it with the Viper, but there are a bunch of packs for 24v for now with the conversion from SLA happening.
Where it gets really annoying is for scooters like the Cuda and Magnus that run on a 44.4v nominal pack. I need to talk to a couple people who actually have these motors and see if the "48v" packs can be used. The "common" li-po packs seem to be 14s 51.8v nominal packs, and LifePO4's seem to be 16s/51.2v and I think that might burn the motor out. Could be wrong, hope I'm wrong, but I hope the next generation of DPV's are going to have a motor adjustment to account for the "popular" voltages to save costs for batteries.