In its SharePoint 2010 version, many people assumed that Microsoft's licensing for its upscale FAST search engine would be be so affordable, it would pose a serious threat to any third party search vendor, from Google to Autonomy. Indeed, at about $25K for a FAST license, it's about as cheap as Google's Appliance. And it's certainly a lot less than you'd expect to pay for a meaningful Autonomy IDOL setup: FAST ESP used to go head-to-head with Autonomy in selections for large enterprise search implementations, and those would often run into the millions for licenses alone.
However, make no mistake: FAST may be a lot less expensive, but it's certainly not going to come cheap. Not in the least bit because implementing it right will still be an expert's job. There's a real risk that your SharePoint integrator will charge you for what amounts to their own on-the-job training. Nor will it be a breeze to keep running -- a lot easier than the old FAST ESP -- but still quite hard, especially at a large scale.
Nevertheless, the main surprise -- as always with all things SharePoint -- is bound to be the total licensing fee. For starters, you'll need the Enterprise Edition of SharePoint, because lesser (cheaper) editions don't support FAST. That also means that for every internal user you'll need eCALs (Enterprise Client Access Licenses). And then, of course, every FAST server needs an additional license, as well.
Microsoft licensing is complex, and becomes even more complex when you're talking about many seats (when you might be able to get volume licensing discounts). Plus, pricing will vary in different regions of the world -- so it's impossible for me to give you exact figures. Most of the cost lies in the Enterprise licensing, which you might already have. (If you want to know what the exact differences are between the editions, Microsoft has a detailed comparison.)
But if I take the various figures given to me in Dollars and Euros (or see this nice example in Pounds), the result is a lot steeper than I had expected. When I run the numbers for a fairly typical FAST setup for 1,000 users, it would cost around $125K extra if you don't already have Enterprise licenses for another reason. (And that's just the licenses, not the specialist work needed to create a good search experience.)
So does this mean you should discount FAST as an option? Not really. Certainly, FAST will quickly run up in cost when you have a large number of internal users, but it's still quite a lot cheaper than it used to be. And its licensing has one large advantage over many competitors: it's based on seats and servers, not the numbers of records indexed. You won't have to worry about your ever-expanding repository of documents suddenly breaking a licensing limit of, say, 500,000 documents. As long as your FAST servers have the processing power to keep churning through them, the price is fixed.
For search, don't just assume FAST will be a cheap add-on, because there are plenty of vendors in our Search & Information Access evaluation research that would gladly undercut Microsoft's pricing. And most of them have plenty of functionality to offer that out-searches SharePoint's basic capabilities, while easier to run and implement than FAST.
So even when you consider search as just one of the moving parts in your SharePoint project, it'll pay to run the numbers and compare the functionality with third-party products. When you do, FAST may turn out to be comparatively cheap, or surprisingly expensive. It all depends on your specific scenarios. And it's not something you'll want to decide off-the-cuff.