I dont know about others, but the build I was using was put out tuesday and was the most recent build at the time of my posting/testing. Trying the most recent build from 22nd shows the same inconsistancies and looking around the beta grid itself i see things with completely insane mesh costs attached to them still. If the costs are in fact down then they are still far far away from where they should in fact be.
Honestly I have to question /why/ they decided to go with some complicated way of determining cost for something that is designed to reduce load on peoples computers. Sure the initial download of the mesh is bigger, but once its in your cache its there for quite some time. Does it really matter if the object is smaller or bigger? Should that really effect rendering cost when an object of similar enormity made out of prims would likely cost less prims and more certainly be exponitially higher in rendering costs? Last i checked there were vew distance sliders in the graphic options for the rare occasion something big in the distance was lagging you. And what in the world does adding a script to something have to do with /anything/. Scripts are limited on an entirely different system and they have never and should never have anything to do with the primcost of an object.
The entire system is busted to the point that you get better returns with a sculpt that takes more effort for the engine to light and render than a simple mesh that represents a much lighter load on the GPU of a computer. Its completely backwards from the way things /should/ be weighted and if this is how the system goes live then Mesh will be almost DOA for anything that isnt an avatar attachment. At this point the only way I can see mesh being at all usefu for bulding is in very limited cases where to many prims are needed to fill gaps between shapes that it bloats the primcost out an insane amount.
We should be /enabling/ people with mesh to do more creative and wonderful things, making SL a less laggy and GPU intensive place in the process. instead we see LL doing all it can to make sure mesh will be the very last resort when building is concerned.