My point was, there is 25.15 BTC worth of incentive for double spend avoiding security in 10 minutes of confirmation on bitcoin. For NXT, it looks like there is jack shit in 10 minutes.
Can you make a better estimate?
You just brought up the main problem with virtual assets located on a block chain and why those projects seem to keep imploding or not really going anywhere. The security of the chain only accounts for the monetary value of the coins. When you make the coins also represent assets, PoW miners aren't receiving a cut of that, so there's no hash power security increase on their end. You then end up with high incentive to attack, and low incentive to defend.
For PoS assets, they're piggybacking on top of the system like PoW, the only difference is that PoS attacks are always far more catastrophic in the long term since coin ownership is network control. Then you have the fact that "ownership" is all defined by the legal system, and no legal system recognizes the authority of a block chain to determine who owns what when tied to assets in the real world.
Hmm.. that is a very interesting point indeed which I hadn't considered, which is more general than talking about any specific chain. Coloured coin users beware. However, one can at least estimate security for assets sitting on the BTC block chain, using the simple formula of block reward = maximum amount you should trust to a single confirmation. Miners don't even know that your one satoshi transfer with 1 millie fee was actually the controlling interest in a multithousand coin company. If the recipient doesn't know you or trust you, they will likely wait a lot of confirmations before acting on the transfer.