Looks like you or your known others in the US go on looking for "CABS" instead of a CAB my friend.
If you check Adwords Keyword Planner, you will see what I am trying to say about CAB keyword any day better than CABS.
- CAB has 74,000 average monthly searches in the United States.
- CABS has 18,100 average monthly searches in the United States.
The comparison to CARS doesn't really make sense, or someone like yourself would come here and start rambling about terms like HAIRS, TVS or what not!!
Request you to at least research a little before sharing irrelevant information like that
The New Guy.
It doesn't matter. The issue isn't google keyword value for some $100 domain that will be parked with some clickthrough ads. This is a $50,000 domain that a million dollar business can be built around. What matters in that case is what the consumer expects with that type of web site. In this case, in the US, plural wins.
Take it from someone born and raised in the US. While people may search for a single 'cab' in a certain city, in the US the natural, cultural usage for a business about cabs will be the plural. Once they know they can use cabs.com to get a cab, they won't search for 'cab' at all. That is the point, and that's why cabs.com was a steal at $50,000.
All these are true in the US:
If someone is looking to buy a car, 'cars.com' is more natural than car.com
If someone wants to buy one shirt, 'shirts.com' is more natural than shirt.com
If someone wants to buy a phone, 'phones.com' is more natural than phone.com
Even though they may type in "white collar shirt", "cheap mobile phone", or "new sports car", what they will gravitate towards in a web site is a plural in all those cases. That is what a business can be built around, and that's why the plural is more valuable if you're actually going to be developing a business around the domain name.
This is the danger of relying on statistics instead of hands on experience, and it's one of the reason I stay away from other country codes and languages that I didn't grow up speaking. There are subtle yet important differences in usage based on plurals and context that can't be taught in any school - you have to be immersed in a culture for quite a while to get a handle on how things like quantity, syntax and phrasing can completely change the value of a name in a certain market.