why do people feel the need to buy expensive cable

I read this thread with interest. One must consider that one ought to consider the issue of cable matching as well. By way of example, an old Naim using DNM precision cables will outperform the Naim using an expensive Goertz cable - why - it's the fact that old Naims can't even be used with high capacitance cables. In terms of food analogy truffle oil on a mushroom risotto will go, whereas however much truffle one uses, it is not going to make a sweet strawberry souffle taste delicious - regardless of how much it costs. One of my best improvements was from a TCI tonearm cable to a Nordost Tyr - it was astonishing the difference that it made. Application is just, if not, more important than the amount you spend, but if one gets the right type of cable and goes up a range the sad truth (in terms of spending money) is that there usually are genuine improvements (subject to the law of diminishing returns)

Interesting discussion. 
I think cables absolutely have a strong effect on a system.
As a general statement, those who have moved up the ladder over time into reference gear generally swear by spending a fair amount of proper cables. My advice to anyone is try a handful of quality cables at multiple price points before settling into a decision. Spending $80k on your system components and connecting them with $1k in cables is false economy and you will never hear the systems true ability. For clarity, this does not mean one must then spend $30k on cabling to do justice either. 

+1 with agreement with referenceaudiomn.

I meant will not guarantee great sound but opens up more options.sorry for typo