Agreed.
I've been looking at the bigger battery packs that can power my cool box for a weekend while camping and am struggling with mega-expensive vs liars. I currently use one I made myself out of a toolbox some electronics and a 110Ah lead-acid battery. To say it is a bit on the heavy side is an understatement!
Have a look around Ali express for paperback casings (about £4.00) to make use of spare 18650 batts you may have, then of course they also have "fill em yourself" made to any size (pricey though).
However it you buy the shonky ones advertised then when you complain next day, you won't need to send them back & you receive a refund, so you might want to cobble something out of a handful of generic polymer slabs you *cough* bought measured & were found wanting ( usb ammeter for £3.00) ..Amazon are fine delivering li-ion via their couriers not so easy sending them back via royal mail in a legitimate manner, thus the write off (for take them but cost is in excess of the value of the goods bought singularly ..which you then review as the pieces of crud they are.
(Get a few people in yr family doing that & you soon have a nice slab to tinker with)