Depends on which Tobias basses you are talking about. There are the original Tobias basses which were pre-Gibson era, there are the Gibson Tobias basses, and there are the MTD (Michael Tobias Design). As far as just 'Tobias' is concerned, the most coveted are the pre-Gibson basses. These go from $3K-$4k (here's one currently for sale here on TalkBass.com:
Pre Gibson Tobias #389 5-string). The new high-end MTD basses are also great basses and can go for $5K+ but these always seem to come up for re-sale. There are also the cheaper MTD basses that are made in Asia. The Gibson Tobias basses came in Basic, Classic, and Signature models with the price being greater, respectively. I'm not sure if these three models were also available during the pre-Gibson era Tobias. I used to have a Gibson Tobias Basic 5 string and it was an awesome bass. It played like pure butter but I sold it because I just don't play 5 strings any more. I've never played a pre-Gibson or an MTD. I also had a Tobias Killer B 6 string. The Killer B series was a "cheaper" model but not that much cheaper. The quality was still excellent. One of the biggest differences was that the Killer B basses have very thick neck profiles (a.k.a. "baseball bat necks"). These were also very good basses but my thumb always felt uncomfortable moving around the neck and holding the neck up. I could never get used to it. However, the Basic, Classic, and Signature models had a thin neck profile and thus these basses played effortlessly.
As far as sound goes, the majority of Tobias both pre-Gibson and Gibson come with Bartolini dual coil pickups and Bartolini 3-band preamps. I am willing to say that the Killer B series probably used a custom winding on the Bartolini pickups because some of these Killer B basses had a warmer burpier type of sound, somewhat similar to a Ken Smith but not entirely -- more like a Roscoe (which uses custom-wound dual coil Bartolini pickups). This sound was not true of the Tobias Basic, Classic, or Signature models. The majority of MTDs seem to have single coil Bartolini pickups in an EMG shape housing because most of the MTDs that I've heard sound like jazz basses. There are also the Tobias Growlers which have a single Bartolini Music Man pickup in the "sweet spot". I've never played these either but they sound great and have always been another very popular Tobias model.
All of the above-mentioned models are available in 4, 5, and 6 string configurations with the exception of the Growler models which are only available in 4 and 5 strings.
Either way, you can't go wrong with Tobias basses. Michael Tobias knows how to make a killer bass.
I hope this helps. Here are some sound clips:
Killer B:
http://www.youtube.com/watch?v=4M6C6svlps0
Basic, Classic, Signature (all three had same pickups and electronics):
http://www.youtube.com/watch?v=jvcja2DVLoI
Growler:
http://www.youtube.com/watch?v=AANGuIeOkyg
MTD (Andrew Gouche Signature model):
http://www.youtube.com/watch?v=VFmP_fRCz5U
MTD (Asian import):
http://www.youtube.com/watch?v=N5sExMEErmA
