Thanks for reporting this. I looked into what's going on and the news is not good. Looks like Amazon really did change something on their .com site (other countries seem to be unaffected for now) that takes away the ability for so.cool to sort and filter Warehouse items by price. After spending a few hours looking for a workaround the best I could do is to bring back the ability to show all warehouse items with the correct prices, but the sorting or filtering by Amazon Warehouse price is gone. Sorting and filtering for Warehouse items will now be subject to the same ridiculous limitation that is plaguing the rest of Amazon -- when you sort search results by price, they are sorted by the lowest marketplace offer on that item excluding shipping, so if the Warehouse price is $3, but there is another listing for $1 with $3.99 shipping, it will be sorted as if it is a $1 item. I am not giving up, but it is not looking good for now.
Yeah I tried searching manually and it's a damned mess, leave it to amazon to break one of the last few parts of their site where low to high actually works properly.
I noticed this last week and was confused, but didn't think much of it and figured it was something I was doing wrong.