I've never seen them for under $9. Even for $5 that is still not a great deal. You can get a 4 pack of 25 watt Wal-Mart brand CFLs for $7. So that's either $5 for 42 watts or $7 for 100 watts. That's a no-brainer right there.
And that 105 watt CFL monster is probably around $30 or $40. While cool as shit, prob the worst $ per watt deal. And if it ever dies, you lose all your light instead of just a small part of it.
The best deals right now are on 23-26 watt bulbs, both for price per watt and lumens per watt. The main drawback is you will have to be jacking with a bunch of bulbs for a decent grow.