Currently the M. 2230 2TB SSDs are $50 off at bestbuy, they're $169.99 - https://www.bestbuy.com/site/wd-black-sn770m-2tb-internal-ssd-pcie-gen-4-x4-m-2-2230-for-rog-ally-and-steam-deck/6551144.p?skuId=6551144

And the 4tb Samsung Pro 990 is the cheapest I've seen at $250 - https://www.samsung.com/us/computing/memory-storage/solid-state-drives/990-pro-pcie-4-0-nvme-ssd-4tb-mz-v9p4t0b-am/

These are the best drives and prices I've seen if you want the most storage for your 16" when it comes in!