Hi,
I can envision then "cheaping out". One airframe saved is XXX megabucks. That loss has some small probability per year. (Decades before one plane went down in these circumstances?) What's the cost in airframes per year for continued search? The risk of "cheaping out" is much the same as above, though. So they are under immense pressure from two sides to not only solve it but to solve it cheaply. I can understand there being considerable deliberation before spending more money in bulk measure.
Cost of a new A330-200F: $194.8 million (official price)
Cost of researches so far (as know by the press) : $28 million