I should spend some time on AliExpress.
For one-off products (that is, one or more of a single item), Aliexpress or eBay is usually (but not always) cheaper than sourcing via an agent from taobao - mainly because of free slow-boat shipping, and you're not paying the fixed minimum agent fees and domestic shipping.
Taobao is cheaper for mixed orders of various products from various sellers at the same time (naturally, trying to get everything from as few different sellers as possible is better, to save the china domestic shipping costs).
For potentially heavy (or otherwise troublesome for international shipping) like these enclosures, I would tend to use Aliexpress because the international shipping will almost certainly be cheaper there than through a TB agent for heavy items, even if it is slow-boat.
I might import from 6 different TB sellers in a single order containing maybe different 50 products of various quantities each from 5 to 1000, pulling that order together on Aliexpress would be expensive and painful. But on another week I might have a need to buy just 100 3.5mm plugs, for that I'd go to Taobao or eBay.