Bad deal for a 12v.
Not bad for a 24v.
Very good deal for a 36v.

I have an extra 24v sittin on my shelf. When my current one and that one goes away, i think Im going 24v Lithium. Still not sold on $500 for start and house though...Sounds funny, those are the ones that I should be relying on.

 

It looks like all the batteries are the same but when they double the volts they halve the amp hours. The 12 v is only a deal if you’re trying to keep it light. No word if any of the 24/36v batteries have a 12v post for jump starting.

 

Probably the same number of 18650 batteries, wired differently for the desired voltage.

I'm not passing any judgement on the Monster Marine brand, but this video is a real eye opener, comparing 18650 batteries from several vendors.

And here's a Youtube showing how they're generally made. To be clear, the Monster Marine brand may have a different configuration (but I doubt it). So the critical issue is the quality of the cells they use, and how well they engineer the BMS (Battery Management System)