I too recently purchased a Sony 52" LCD (KDL52W4100) and got the same spill from the sales rep from BB. "You must buy this HDMI cable (pointing) to receive full 120hz blah blah blah." I told him I would find one online cheaper than $150, so no thanks. I mean, you've got to be freaking kidding me trying to push another $150 on me after I just spent $2400 on a Freaking TV! Greedy bastards.
Anyway, the story goes (although this may not be the case 100% of the time) is these guys (and girls) get hired there not really knowing much. Sometimes they're like me and "think" they know a lot, but when they finally get in the world of electronics and computers, get their eyes opened wide. I started working at CompUSA @ 19 (about 8 years ago) and I'm not one to go telling somebody something that I know isn't true, however I was unaware that half the time I was telling people things that I didn't know was false.
What happens is a manager or a "more advanced" team member will tell you something to this effect, like "Your surge protector must be 1028 Joules", and you, the ignorant one, says "Oh, really, I did not know that". Now you are passing that "knowledge" on to anybody you talk to. This is just one example (still not even sure about the truth on that one), but the cable thing is a bit rediculous. Even though I didn't know everything mentioned in this post, I did know that any cable bought at Walmart, Circuit City, BestBuy, hhgregg, etc. were all marked up over 800%. I remember one of the last things I bought with my employee discount at CompUSA was a SCSI2 cable that retailed for $74. I got it for $4 (cost).
It's really sad how high they have these marked up and even with the number of places on the web to buy these, they still have not brought these prices down. It's just sickening.
I'll be honest though, I have had some guys tell me "Here's the cable you need, but you can get it online for much cheaper." I like these guys and stores listed above need more of them.