Aside from cost there are far more factors *against* voice acting, such as having to lock content at some point to have a clear copy to the actors, and then not being able to change it anymore.
Heck, the EE would have been hell if the whole game was voiceacted since all the added stuff, changed stuff would have required a full re-voicing, and if the actors weren't available they need to re-voice *everything* for that character. Compare them with just adding more branches now.
Also Larian was basically adding and writing to the game till release with D:OS. Due to the lock that I mentioned before Larian wouldn't be able to do that this time around, if they went with full voice-acting.
More negative sides of full VO is that mods will stick out even more since they will need to do equal voiced characters or stick out as a sore thumb. And getting VO for a mod is NOT easy, take my word on that (and if you won't just google 'my' mod "M4-78EP").
Also funny you mention BioWare since I'm pretty sure it hugely bit them in the back with The Old Republic (100+ million dollar budget IIRC, and that was even with a lot of alien VO surplacing human VO).
So in conclusion I can only say "no, no, no, no"
Just compare the amount of text in, say, Pillars of Eternity (not full VO, even if they voiced too much *everyone agrees!!!*) to a BioWarian game. That's like comparing the Lord of the Rings trilogy with a 150 page teenage romp. And then claiming it 'improved'...
You are confusing SWTOR with KOTOR... the 1st is over 200mil.. the other most likely under 15Mil.
Not sure how Larian makes their voice acting but on other companies devs make contracts with actors for X years.. and make it that they are open for future dubs.. You see this in Mass Effect, they released DLC after the game and all the actors voiced recorded.
In every dev cycle content has to be locked at one point you can't write more quests because it will take more artists or you have to stop programming features to build quests and polish the game around it. There are multiple stages and content is locked for various dev groups while making a game. Further more writing and voice acting is usually linked and both are improved by working together.
You make little to no sense.. it's just another layer on the development, the hassle is more financial that a burden to development process.
