If you can get Hamels for 4/98 or Lester at 5/130 and keep your prospects, you get Lester, 10 times out of 10.
The thing the Sox are going to do is assess the FA market and the trade market. They're swimming in both dollars and prospects. The FA market is absolutely flush this year in SP, but bats are nearly impossible to come by on the FA market.
So, I would imagine they will attempt to fill the SP needs via dollars and fill any positional needs via trade. That would make sense. Why would you trade for a Cueto when you can sign a Shields? Cueto is younger, but you get him for 1 year then you're faced with the same delimma as you had w Lester.
If they want to sign Lester AND go after Hamels, I guess I could see that. I would love for them to stand pat on their offense, give Lester 5/25, trade for Hamels (WMB, JBJ, Ranaudo, and absorb the contract should get close - see: Price, David), then fill up the bullpen with Miller, Koji, Taz, Hochevar, Webster, Badenhop, and 1 more.
That would eat up most of that $75mm if they gave Koji a QO ($15mm), and gave Lester and Hamels $25mm each (or an average of that between them). Give Miller $7mm, Hochevar $5mm, and there is $77mm right there. Perfect. Now go win a WS.