The point of diminishing returns is different for every budget and every system.

Ditto Jan's comment but I found the upgrade to the King Cobra ICs to be well worth the money. The Type 4 speaker wire is also very good, although I can't say I've demoed the others in the line. eventually I went up to Stereovox Firebird speaker wire which I felt to be significantly superior on all fronts- and about 3 times the price.

A lot depends on your system. The better the system, the more likely you are to hear subtle differences in cables and the harder the choice becomes. A friend of mine just spent 3 weeks auditioning 27 interconnects until he finally settled on the one that made his system sing.

These cables would not make nearly the impact on my system because my rig would not be able to resolve the differences to such an extent. So, in my rig, they would all essentially sound the same, whereas in his, there were quite profound differences.

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I am curious if the benefit/cost ratio starts to diminish from here..

You kind of get the best benefit/cost ratio when the item you buy (something you can afford) is top of the line or near top of the line from a particular vendor.

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You kind of get the best benefit/cost ratio when the item you buy (something you can afford) is top of the line or near top of the line from a particular vendor.

And your justification for this is what? You will be less likely to hear the improvements of top flight cables in a budget system. You would be unwise if you purchased the 1k watt amplifier (from a company that had a 2k watt version) for your Klipsch LaScalas. A $4k cartridge on a Rega P9 wouldn't be the best choice.