Most coins don’t operate in the costly business of providing a hedge for BTC.
As Nu has no re-insurance for BTC volatility and successful hedging, it can be expected that trading with a close spread leads to a loss.
A spread would need to be a function of trading volume and volatility to have a chance to make enough money to pay for the costs like costs from hedging, exchange default, opportunity costs.
Other coins just have a blockchain running, which provides incentive for processing transactions. The rewards for processing the tx are more or less created from thin air. But they follow protocol and you can make calculations about the ROI for providing efforts.
Be careful. You can game the market of NSR.
- Buy NSR.
- Buy NBT.
If the reserve threshold is 50%, buy at least as much NBT as are currently in circulation. Adjust the amount of NBT according to the reserve ratio, if it’s not 50%.
- Trigger NSR buybacks.
- Sell NSR.
- Dump all NBT, empty the reserve and trigger an NSR sale.
- Rinse and repeat.
The problem here is: this doesn’t follow a reliable protocol.
The reserve ratio etc. can be adjusted at the whim of the (Vice) Chief of Liquidity Operation.
If you have an appetite for risk, you may try 
It’s less risky if you can take shortcuts.
For example if you can skip the “buy NSR” part, because you received a load of NSR as “angel investor”, although you might never have had to pay a single Dollar for them.
Ah, of course all I say is tinfoil hatter’s craziness. Don’t take it serious 
But can you tell me the total amount of Nu’s dev fund? Did the seed investors really pay for the NSR they received? Or was that a farce to provide the base for a double-tracked project, one in which the architect couldn’t lose, but only win this way or another way?
It’s hard to tell, because little information about that is publicly available.
While I need to make an effort to think of such crazy stories it would be little effort to debunk all that, if only there was a public and complete accounting of this most transparent corporations that has ever been created.