There are numerous on-line "shopping" aids to ecommerce.  Kelkoo, Ciao for
example.
Does anyone know how they determine whether items listed on the suppliers'
websites are actually in stock.  What I'm thinking about is the website of a
supplier where the (attractively low) price of a new camera is listed, and
no stock level is indicated.  Some of the search engines indicate that the
item is in stock at this supplier.  How?  By emailing the vendor? Surely
not, or is the "in stock" indicator simply a guess, so as to generate more
hits?

On many sites supplying the computer trade, their sites frequently list
local stock levels, and quickly replenishable stock levels from a central
store.  I've never seen this done for cameras.

Puzzled.