mogami is NOT expensive. if you think it is, check out zoalla or van den hul.
i tend to go for the mogami/neutrik cables myself. i got tired of cheap cables failing at the worst possible moment. decent cables like mogami last a whole lot longer, especially when repeatedly unplugged and such. you can either buy decent cables and get 10-15 years out of em, or you can buy hosa or jade or something and replace it every couple years, all the time worrying about when it's going to fail (b/c it will).
i hate buying cables, so i'd much rather have something that lasts. plus, it's a whole lot easier to work on a mogami/neutrik (or switchcraft) than something that's got molded ends like hosa.
soundwise, there's a whole lot more factors in my studio that i have to worry about than the patch cable between the mic pre and compressor. i buy decent cables b/c they're not cheaply made and i can work on em if needed.
guitar-wise, i did notice a difference (an improvement) when i switched from planet waves type cables to monster, but i largely attribute that to the thicker cable and the extra shielding rather than the pseudo-science they peddle on their website. the buzz/hum was gone and that was #1 for me.
but really, it's like everything else.....buy cheap, buy twice (or more).
cheers,
wade