Its hard to argue that kyle isnt at very least one of our top 3 players. Within the salary cap contraints, it is quite possible to have these three on at least £250 k, so i doubt it is all about money.
My guess (and thats what it is) is that Kyles agent (not kyle) wants a relatively short term deal, ie 2 years again and Sir Mac wants 4-5 years as he wont want to go through this in another 18 months.
Kyle isnt (yet) the superstar Jason robinson was when he changed codes, so the money from them wont be ridiculous, but if he had 2 amazing seasons it might be.