Quoting: crankshaft
If he's coming with an extension the price goes up. Not Krav but it will take Lundkvist.
He can only be traded to 3 teams due to his NTC.
He can effectively choose his destination if two of those teams aren't willing, don't need, or are unable to acquire him.
Unless he opens up to more teams, there may be no bidding war or even options for SJ to pursue, so he could very well go for less than market value. Just look at how Buffalo was forced to move Hall to Boston for a mediocre return.
Part of the value of a rental is also residual. Teams have the option to re-sign that player. If he will only sign an extension with one team, the others will be willing to offer less, and the acquiring team can lower their offer as a result.
It's not a given that he will even get market value, let alone added value with an extension. It isn't always that simple.
He could turn out to be yet another example to GMs of why you should be more selective when handing out NMC/NTC's.