Logos usually need to appear in print in any number of contexts, sizes and so on, as well as on the web, in video overlays and just about anything else you can think of. That means that resolution has to be taken out of the equation. More often than not, logo design involves manipulating type -- not just using it, but changing the shapes of letters, often in very subtle ways. Professional designers, therefore, tend to use programs that work in vectors rather than in raster space (pixels). It wouldn't be a stretch to say that Adobe Illustrator is an industry standard.
Yes, it's expensive, but you were asking about professionals, and professionals tend to spend as much as they need to spend on their tools. They do that for a number of reasons. First, they don't want to be caught out with missing features; time is money, and the last thing you want is to have to blow time that should have been billable to a customer either trying to figure out a workaround for something that should have been simple or shopping for an add-on, utility, or another whole program to do a part of the job. Second, they need it to integrate into their overall workflow -- elements created in Illustrator can easily be imported into Photoshop, Fireworks, Dreamweaver or InDesign (all part of the Creative Suite) as well as 3dsMax or Maya for 3D work and After Effects for video without a hiccup. Finally, they need to be able to rely on a community of other users in order to quickly turn a concept they don't quite know how to realize into a product as quickly as possible. Again, the expense up front saves time in the end, and that means that the tool pays for itself in short order.
Now we come to reality -- you are not yet a professional, and unless you're set up in a way that most people aren't at your age, you probably don't have a couple of thousand dollars lying around that you'd rather spend on design software than anything else. That means that the Adobe Creative Suite is probably out of your reach (unless you resort to piracy, which I'm not about to encourage). That's okay -- all you're going to miss out on, really, is the workflow aspect. There is a FOSS (free and open source software) answer to Illustrator called
Inkscape. It is to Illustrator what the GIMP is to Photoshop -- a little rougher around the edges, obviously designed by programmers for programmers rather than being polished by designers for designers, but all of the major features are there, and there's a decent online community. You won't be able to simply drag and drop things between your drawing app, your painting app, your publication design app and your web design app, but you shouldn't be worried too much about saving a few seconds here and there at this point in your progress. If you catch the bug and decide to go pro, you can pay for the power tools as you can afford them.
---------- Post added at 07:27 PM ---------- Previous post was at 11:53 AM ----------
I should probably add, at this point, that while the GIMP is "good enough", it's not really good enough. At least not as it stands at the moment. To say that a person working in the graphics realm professionally who uses the GIMP is a bit, um, eccentric would be a bit of an understatement. While the GIMP is certainly capable enough for some things, and even adequate for occasional use, there are a lot of things that prevent it from being a real professional tool. Not least of those is its colour handling. The GIMP is (as of this writing) limited to an 8-bit-per-channel colour space (GEGL is supposed to get around this eventually, but it is only partially implemented in current releases) and that means that curve corrections, gradients and non-destructive editing are all affected by mathematical limitations. I'll send you to a current discussion over at
Hacker News (which, by the way, has nothing to do with cracking, warez, "hacking" in the colloquial sense or anything of the sort -- it's the news aggregator for the Y Combinator start-up funding community, although the name may trigger filters if you're trying to get there from a school, work or library computer). That's not meant as a discouragement, but as a sort of "if you run into the GIMP's limitations, you're not done -- there are tools out there that can do the job, but they're not free."