Most Cisco SFPs and GBICs are a rebadge of another companies' product (not a Chinese company, either) which can be bought from the original manufacturer in batches of 100+ for well under AU$100 each, if you know who that is. There are only a couple of major optical manufacturers in the world. However if they were manufacturing them with the Cisco ID PROM and selling them other than via Cisco channel, that would be a different issue (some combinations of Cisco device and software will refuse to operate with a GBIC which reports a non-Cisco ID, but those are rare, as major customer pressure Cisco to open this up on more popular platforms).

The most significant recent grey-run which I've heard rumours of on Cisco products related to something much more expensive - 6500 components (DFCs, line cards, etc).