I bought some blank cassettes from eBay US, after getting my recent cassette deck last month. Metal cassettes are four times as expensive as chrome. But they are both available. And at about $3-4 per chrome cassette, I found the price excellent.
Then I accidentally stumbled upon www.tapeline.info in the UK. They have bulk cassettes, chrome type, at unbelievably low prices. These are "unbranded" or "assembled". Some customers are saying that the stock is identical to BASF chrome tape. I've ordered a few. Let them arrive -- I'll let you know how it works out. If this source works out, I'll not bother with branded blank cassettes again.