Hard to say. I voted for 50%, but that's only because the amount of raising has been steadily going up.
While we were playing at low-levels (roughly 1-7), every death was permanent, with only one exception. At these levels, even the 5,000gp cost for Raise Dead is a serious drain on resources.
During the mid-levels (8-13) this started to change, and roughly half of the people who died would be revived. Death was still a serious problem, especially when caused by [Death]-effects, since those required a Resurrection. Cost was also still a big factor.
At high levels (14+, currently playing with 7 PCs of Lv19) everyone is revived, especially with the availability of True Resurrection, where there is no longer even a level loss involved. At this point if a character dies, and the player wants to try a new character, the PC is revived and retires shortly afterwards. I think it's just a matter of not wanting to feel like you've "lost" to the monsters/NPCs/whatever.
Personally, I'm not a big fan of this sort of play, since death seems to have lost all meaning. However, since we have very different opinions on this matter within our group we've decided not to worry too much about it and just have fun.
We've started this campaign over 5 years ago and rotate DM-ing duty. Some people have more trouble with killing PCs than others. My turn has come up to DM, and I don't really have a problem with killing a PC, so we'll just see what happens
