The Smith & Wesson "Classic" 27 is what Smith is currently selling in nickel. My best guess is that you'd have to shell out somewhat north of $900 for a new one. However, older models will sell for less, depending on their condition. Many of the revolver fans on this and other forums think that the older models are better than the new ones (I'm not one of them). What you buy is definitely a question of taste, however.
You may not be aware of this, but Smith signified changes with a - followed by a number. Thus, a 27-2 signifies the second engineering change in the Model 27 line.
The price of an older gun depends on several factors. First, collectors look for certain series and even specific barrel lengths within a series. Second, the conditon of the gun, including its cosmetic appearance, can greatly affect price. Finally, collectors seek guns that come in their original boxes with documents and accessories, like cleaning sets.
Most sought after in the 27 series is the Model 27-2. That doesn't mean it is necessarily the "best" gun out there in the 27 line (collectors would give me an argument about that, I think) but it is definitely the most sought after. Also highly prized is the so-called "pre-27", a model that came out before Smith began putting series numbers on its guns. And, most expensive of all are the "registered magnums", the precursors of the 27 series that Smith began marketing in the 1930's.
A 3 1/2 nickeled 27-2 in excellent condition, even without box and papers, is a pricey gun. One of those may very well set you back over $700. On the other hand, other versions of the gun cost less. Last year I paid just over $500 for my 27-3, a very nice four inch gun made in 1988. I bought it as a shooter, not caring about its collection value.
If you like N-frame .357 revolvers, like the 27, but you're interested in a shooter rather than a collector's item, you should definitely take a look at the Smith & Wesson Model 28, or "Highway Patrolman." Smith made that gun at the same time that it made the 27, and it marketed it as a police revolver and as a less expensive N-frame .357. There are cosmetic differences between the 27 and the 28 (the finish on the 28 is duller than that on the 27, and the 27 came with a checkered top strap whereas the top strap on the 28 is plain). But, mechanically, the guns are identical. I have friends with 28s and they are very, very fine guns that shoot just as well as the Model 27. A good condition 28 will usually cost at least a couple of hundred dollars less than an equivalent 27. However, 28s were only made with blued steel, never in nickel.