It's not the "star" part that matters, it's asset value.
Building a roster is an exercise in multi-period constrained optimization, you have a salary cap, a limited number of draft picks, etc.
So you have to factor the value of the player, the fit of the player and the player's cap cost.
The most valued assets are quality versatile players with attractive contracts, that is, players who can fit multiple roles (increased optionality when adjusting to stochastic events, i.e. injuries) - ROR is a good example, so was Schenn, a D-man who's comfortable playing both sides, etc.
Players who are harder fits have less value (i.e. a player with significant value based on PP1 play, for example).
Players on one year contracts have limited value, you're only getting the one year, if you have to extend them at a cap hit above their value (pay UFA prices) then the extension has almost no trade value (you paid for it in salary).
The ED adds another element, adding a player you must protect means losing a higher quality player (because you're pushing a better player off the protected list island), so that loss of expected value should be factored in.
A good GM takes into account all these factors in deciding which players to trade for and how much to give.
#11 is ED exempt and cost controlled to some extent for possibly a decade (ELC, RFA contract below UFA rates).
You don't give an asset like that for a one year rental.
