Vivienne Daguerre has an article up on her blog about Cloud Party starting to rent sky islands. See: Private Islands Available in Cloud Party.
She does a good comparison between Second Life® and Cloud Party®. Pushing the numbers into a different format the land-wise cost per square meter is better. SL=US$0.0046/sq meter – CP=US$ 0.0015 that is about 32.5% of the cost in SL. As you get more land in CP the cost goes down to $ 0.0004/sq meter which is about 1/10th the cost.
Tier is another thing. CP has limits on how much stuff you can put in an island. But, I don’t see a tier costing system just limits. The 100×100 meter islands are about 15% of the size of a Second Life region. One can have 350 objects, 25 of which can be dynamic, and that total up to 300,000 triangles.
It is hard to compare that to Second Life. But, 15% of 15,000 prims is 2,250 prims. Trying to turn that into triangles is reaching. Regions can handle 750,000 but I think that is an average… and it is from my memory which is sometimes unreliable. (See SL Limits) But that gives a limit of 112,500 triangles… but it is possible to create a million polygon avatar in SL… so, the polygon comparison numbers seem rather meaningless.
There are no adjacent islands in CP. Also, CP is incomplete. So, it may be reasonable for the land cost to go up as development continues. But for now it is a pretty good deal… provided you don’t compare it to OpenSim, but that gets complex.