FLCL is a direct to video, quirky artsy title aimed at older fans. Death Note is unusually good, fairly long Shounen Jump suspense show with an interesting hook aimed squarely at the mass market (ok, mass *anime* market in the UK, a little different). A lot of anime watchers will not "get" FLCL.
If they released every episode of FLCL on one disc, it would still not have as many episodes as one pack of Death Note. If they halved the price too, they'd make no money on their release at all. They can't win, so they're instead taking the highly reasonable business plan of trying to release it in a way that balances value and profitability so they can afford to release more crazy Gainax stuff.
We still get twice as many episodes per disc as the Japanese did for almost half the price (remember, it was an OAV so it wasn't televised when it came out; they had to buy/rent like we do) and double the language options. I really see little room to complain.
As for choice of months - well it's hard to avoid Death Note, Naruto or Bleach entirely as is at the rate the Shounen Jump series are churned out. And any TV series disc will have more episodes available than FLCL got in its entire run. They're not hoping to outsell the major shounen fare. They simply won't be able to. It's aimed at a different type of fan.
I'd buy FLCL over Death Note if I didn't already have the R2Js (preordered on release as imports and I don't feel ripped off even now it's cheaper; love it).
R