That does sound like the valve stem seals to me, I know mine are shot and it will do that every other start
Also if you have it sitting there idling for several minutes and it begins to puff blue smoke that is also another sign the VSS's are shot, something to do with the vaccuum or pressure in there dragging oil past them into the cylinder, someone else can explain it better im sure
As for cost Hopefully someone else will know as I have not looked at getting mine replaced as yet