One strategy might be to signup as many free 10 SP accounts
The free offer is "$10 worth of SP" (i.e. 3 SP at present) not 10 SP. The 10 SP may have been the offer at one time but not any more.
Ah I see. So the point remains that users need to want to stay on the site, else they will have many abandoned 3 SP accounts.
No doubt. Of course nothing prevents those users from coming back later to claim the accounts if the value goes up. There is no maintenance cost to idle accounts that don't use bandwidth.
See the edit on my prior post.
Price going up doesn't help them reach 30 SP easier. Actually it may become more difficult as more bloggers will be competing.