this program is XNA exclusive
Nothing so far released regarding RBN and the Rock Band Creators Club indicates that it will require XNA. XNA Creators Club != XNA Studio, XNA the programming language, XNA the flamethrower, etc.
Details about Magma, which packages the songs for distribution, haven't been released; all Harmonix says is that it's a "PC tool." That means it may require XNA, but for all we know, it equally might require Java, or COBOL, or shoving your head up your ass. There's just no information yet.
it's also $1,000 to get started ... If you own a PLAYSTATION 3 and a PC running Linux, or if you own a Wii and a Macintosh computer, you also need to buy an Xbox 360 and a PC running Windows.
Ignoring the suggestion that a Mac owner or Linux user has to buy another computer to run Windows, you're looking at about $640-$850 ($230 Xbox Pro + $150 Windows license + $100-$150 360 Rock Band set + $100 Creators Club + $60-$225 Reaper license). Reaper has an OS X build and works in wine, but since we don't know anything about Magma, it may well require Windows. If not, the cost of entry drops further. If your band or label makes less than $20,000 gross/year, Reaper costs $60, not $225.
At $80, selling their songs at the standard small-label price of $1/80 points per song, the band would have to sell about 2,650 songs to recoup their investment, before taxes. At $640, its 2,133 songs.
Sounds daunting, eh? Dropping $640 with no guarantee of profit? If you're just putting on 2 or 3 songs, you could probably hire a ScoreHero forum person who has a few years' experience in charting to put it together for $200-$300, or less, who knows.
There's no accurate sales figures for Rock Band DLC; Statosphere used to attempt to estimate them based on leaderboard activity, and the song that had sold the fewest copies as of Sept. 2008 (Devo's "Through Being Cool") sold an estimated 2,895 copies in three weeks at $2/sale. MC Frontalot moved an estimated 3,445 copies at $1 each of "Livin' at the Corner of Dude and Catastrophe" in one week.
The worst-selling song, The Runaways' "Cherry Bomb," was available on opening day and sold an estimated 13,550 copies in the first 11 months of Rock Band's existence; projecting that performance onto a RBN release, that'd be a gross take for the artist of $4,065, at 30 percent of each $1 sale.
Don't take any of this for any significance - IANA band's business manager, the DLC stats above are sketchy at best, and it'll be a much more crowded marketplace full of songs that will, on average, have lower-quality audio and note charts. But 1.) it's not $1,000 for gear, and for most small bands and some small labels, it won't be $500, and 2.) there's a decent chance artists and labels with a fan base and dedication to quality and promotion can break even.