"Price" for LJ? Are you referring to money or what Dallas would have to give up (potential high draft choice and a top reserve)?
I'll address both.
Monetary "Price"
The amount of money LJ is seeking in comparison to what Faulk sought in the late '90's is all relative. The league signed a new TV contract and is making more revenue, teams now understand how to manage their cap and there is more cap money available thus the current wave of players are breaking the bank. (See: Leonard Davis, Derrick Dockery, Nate Clements, E. Steinbach and Dielman). In the late '90's the contract that Marshall sought and was paid by the Rams made him one of the top paid players at his position if not the top paid RB at the time (7yrs $45.15mil). As of August 5, 1999, his contract was "by far the biggest contract in Rams' history...." according to John Shaw Rams Team President at the time. That is exactly what LJ seeks except now the top RB makes tons more than what he made in the late '90's.
Potential High Draft Choice AND a Top Reserve "Price"
The Rams got Marshall for a 2nd round pick and a 5th round pick. In hindsight that was highway robbery. Just like when Dallas fleeced Minnesota. The NFL is a league where teams attempt to not get burned like another team did years prior thus the asking price will be higher the second time around. The Chiefs don't want to be sitting there looking like the Colts did after they traded Faulk in April 1999 only to watch he and Kurt Warner hoist the Lombardi Trophy that same season. The Chiefs will ask for the kitchen sink if they could but that doesn't mean that is the final request for consideration. They may very well end up having to settle for a conditional 2nd that can become a 1st if LJ meets certain incentives and a second day pick.
As I stated, I wouldn't commit to the trade as presented (Cleveland's pick plus MBIII) but if they came down like I suspect they may have to, I would consider it.