Olive is barely cheaper, at all! (not to mention the proliferation of eco vero or whatever it is and polyester).
I also think Kin is more attuned to an oversized version of COS, aesthetically, than Toast - there's nothing crunchy or organic about those shapes.
I would honestly try Ebay. I have made most of my favourite purchases from Toast and similarly priced brands this way. In the long term, i f possible, it might be better to save for one good, higher priced item than a pile of them from a cheaper, less well made brand.
However, if you prefer to just play with the aesthetic without the cost, I'm not sure outside of buying second hand, and many are as new.
Carrier Co are worth a mention - much less stock and not remotely fashion focused, but somewhat more modest and realistically priced.
For good knits Finisterre do lovely Donegal and wool stuff, but whilst a bit more affordable, they're still not cheap.