Re: Forget the discount
Agree that you go in with your eyes open, and egress is a bit of a pain - but only a bit. Regardless of cloud provider, there are many ways to get your data out again. They do cost so should just be considered as part of the broader ROI. If you just take storage as a simple example, any company/govt considering cloud should look at the costs of themselves managing, maintaining, fixing, expanding, replacing disks, disk arrays, fibre networks and compare this with the costs of storing the data in cloud and pulling it out if necessary after X years.
Same consideration for using a GSI in a traditional outsource - yes they look after the managing, maintenance, etc (and charge for it obviously), but they WILL also charge you to get your data out at the end (you may have negotiated this as part of the contract run rate, but you can bet that you ARE going to pay for it), along with any stranded costs related to hardware that the GSI has not been able to fully depreciate within the term of the agreement. At least with cloud these charges are fully transparent so you can work out the true TCO and make an informed decision.
So basically, what I'm saying is, yes, there are costs at the end if you don't renew, but that is only part of the consideration you make when considering any large IT project/hosting contract. As you say - eyes open.