The game has been patched now, you can no longer clone chests for methods before.
If you have a save from a while back when it took anything from 2-8 billion to unlock and didn't get the trophy you can now with this patch go into a world break something to earn studs and the trophy will unlock as long as you have over a billion.
The other thing with this patch is you no longer have to do this trophy in one session like before.
This isn't really a solution as to how to get the trophy because it's been bugged for a long time, I had a billion a very long time ago and have been waiting for the patch to fix it which only came out yesterday.
The legendary bricks are your best bet because they give out 60,000 studs per chest.
Any comments or negative feedback please let me know.