Like with everything else, as games have got more complicated and standards have gotten higher, it means its much harder to do stuff decently, so voice acting is, I suspect, increasingly expensive to do a job which is not as bad as the previously mentioned sat-nav voice. Bad voice acting is worse than none, too, I suspect.
I lived through an era where adding voice acting was a case of "go find people in the office who don't sound terrible and have them line-read". "King's Quest V" on CD-Rom was one of the cases in mind...
(They did so much better for the next one.)
Worse off was 'Stonekeep' which wound up being just cheesy enough to be tolerable.
But, yes. Good voice acting hinges on not just finding good actors... and affording them. (Note: this does not mean you need BIG NAMES, only people who can do the part. See also: Matt Shimkus as "Sokolov, the Space Russian" on Death From Above... versus Sam Riegel as "Shamrock".) It also means having a good
voice director. Talent doesn't matter if the director is dropping the ball on some cases (most early English Dubs for anime - the actors can make it work, but the direction was bad).
It's a small peeve of mine (not a pet, this one's
practically feral) about people expecting voice acting to be present and awesome all the time - even in smaller-studio games. For every one of those which had point-on voice work (hi 'Hades') there's others where it didn't work out so well... but I've had conversations with friends who know "the industry" of voice acting and pointed out repeatedly how it's NOT as simple as "hire people, hand script, get quality". It's not that it's necessarily expensive (up front) but it is time-consuming... (which makes it more expensive over time).