Can you cross-reference your anecdotal friends by how much 3pp stuff they have bought in the past?
This ended up pretty long and rambling... using s-blocks to avoid the Wall of Text effect.
But to answer the question,
[sblock]The majority of my sample consists of dudes who play Living Forgotten Realms (LFR), the 4e RPGA campaign. At the store where I play, there is a good sized group, about 30 people. About one-third are old-timers (started with AD&D 1e or earlier), one-third started with 3e, and one-third are new to D&D.
Note that if you exclusively play LFR, there is very little reason to buy third-party stuff
for 4e, as you can't use it in LFR. But, that said... and bear in mind this is pretty speculative on my part, and I'm going to use a lot of weasel words so you can't pin me down on anything
* 9 out of the 10 old-timers regularly bought third-party stuff in the past, especially during the 3e days. There is one bad-tempered guy who "refused to buy any of that crap", and goes around griping about why we aren't playing 1e instead... I'm not even sure why he plays LFR, frankly. I think because his friends do.
* 4 or 5 out of the 10 3e-era guys bought third-party stuff. They had some kind of ongoing (3e) campaign at the game store, so they were exposed to it all the time anyway. Of the other half, I think they knew about it but just weren't into the game enough to buy much more than the 3e PH, if that.
* 0 out of the 10 "new to D&D" guys used to buy third-party stuff. Obviously.

But technically some of them have bought third-paty stuff for 4e: that one-buck adventure that Goodman (?) was selling, and Level Up magazine (also prominent in the store).
Now, you wanted to know how this matches up with "use of the CB", so here goes.
* Old-timers: I think all but one of them (us) use the CB, even the angry guy. Perhaps it is because this group skews older, and has been playing longer, so we don't get as much of a thrill as we used to out of laboriously filling out character sheets by hand.
The one guy who doesn't use the CB is the local Point of Contact for the LFR! Go figure. (He uses some character sheet / power tracker he found online and writes it out by hand.)
* 3e guys, subset who bought third-party stuff: hmm... two definitely use the CB, not sure about the other two or three.
* 3e guys, subset who didn't buy third-party stuff: again, I think two or three do use the CB, the others don't.
Of the ones who don't (both subsets), "don't like the format" is the most frequent complaint I here.
* New with 4e guys: now strangely, only 4 out of the 10 seem to use the CB regularly. I think some of the others started to when it was free (beta), but didn't want to shell out for the DDI subscription. But honestly I don't know the newbies that well (big age difference), so I'm not sure why they don't use the CB.[/sblock]
And if you can, could you compare that with what camp they are in among your sample reasons not to use the DDI: won't pay, don't like DDI/CB and/or prefer alt output?
Kind of answered above, but to put another spin on it:
[sblock]* I think "won't pay" is primarily a factor for the new-with-4e guys, because they are younger, less committed to the game, have less disposable income, and more free time to spend filling out character sheets by hand. They would rather spend their X dollars / month (that would've gone towards the DDI) on beer or movies or whatever.
* I think the "prefer alt output" is primarily a factor for the old-timers and the hardcore 3e-guys. We've been around, we're used to memorizing rule, so we don't need the full CB power card output, just something to trigger our memories, and the relevant math. The CB output has
too much information for our old, tired brains. However! We do have the disposable income to pay for the DDI, so we probably use the CB to check our math.
* I think the "don't like DDI" isn't much of a factor for the crowd I play with. By definition, it's a 4e crowd, so those who
really dislike the DDI (and by extension 4e) are not in the sample.[/sblock]
= = =
Now one thing I touched on above is the RPGA. As a third-party publisher, this is basically an impossible market to get into, because by fiat an RPGA player can only use official content (meaning WotC stuff).
But there are two reasons for a third-party publisher to hope. (IMUO -- U = uninformed.) One, I think the number of players who
only play RPGA is pretty small -- anecdotally (again) the vast majority are also in an non-RPGA campaign. So you can still sell them stuff to use in their home campaign.
Two, you can take a page from Paizo's book and make your own organized play campaign. (Maybe. I have no idea of the legality of doing this with 4e, nor do I really want to speculate on that aspect.)
Or, make it less "organized play" and more like what WotC used to do with the Dragon magazine adventures: have a way for the players and DMs to report when they've played one of your third-party adventures -- which of course has tie-ins with other player-focused products you sell -- and then give them some kind of tracked "points" or "frequent gamer miles" that they can trade in for goodies of some sort.
Again, I think if you give people a sufficient reason to buy (and use) your product, the barrier posed by the CB can be overcome. It's just a matter of finding something that appeals to people enough to get them to overcome the annoyance of not using the CB.