Given only the task "move a VPS from one hosting provider to another", "rand(1000000)" is a decent estimator. ;)

But seriously, there are an incredible number of variables in this situation. Here are some I've encountered moving VPSes:

* is the code in source control?

* is the ACTUALLY RUNNING code in source control? This is different from the first one.

* how many services are running on the VPS? Moving a PHP webapp is one thing, moving a multi-process app that's using multiple daemons is quite another.

* has anybody documented the setup? Little changes in /etc can make a big difference.