Markov even at his age seems to be able to give another good year to the habs (look at his offseason work and last season production). If the habs improve on their PP, Weber is a lot better than subban on that regard and the addition of mueller helps, you can see either Markov or Beaulieu get a spike on their overall production. It will most likely be Markov. So, in all, Markov prob gives u another season of 40-50 points as a 37 year old and easily fetches a 1rst round pick and a good prospect. He has the experience, the respect, hes a rental and past deadlines have been massive over payments.
As for plek, look at vermette and Erat for comparables, a 1rst round pick plus a good prospect starts the negotiations.