Thing is, a cheap bass (under 100 bucks on CL) still sounds infinitely better than any bass synth I've ever heard.  I'm not a search and sample kind of guy so maybe I haven't heard really great synth sounds, but seriously, I was amazed how easy a deep, rich bass sound was from a real bass guitar.  You can spend money if you want to, but you really don't have to spend much to beat a guitar trying to sound like a bass.  I'm the poorest musician on this forum, I'm pretty sure, and I did it for under a hundred bucks.  
 
And the time a real bass saves you, too...I mean come on, that's worth its weight right there.  Who wants to point and click for hours when you can knock it out in 10 or 15 minutes actually playing?

As for time, it depends on your skill level and what midi input methods you have available to you.  I struggle with a lot of string noise when I am releasing the strings from a fret which reduces my confidence when playing.  I can input bass synth parts very quickly using a midi keyboard.  I bought my bass prior to moving in the box (I used a BR600 digital recorder to record tracks and mixed using GT Pro 3 and 4.)  Then I bought my bass and shortly after moved into the box.