Face to face selling is also far more effective since your fans can get to know you as a person so they have more of a reason to buy your art. Sounds weird, but having a personal connection to a REAL living person can be very powerful! Meeting someone in person allows us to want to emotionally support them even more than if they were a faceless artist online whose art we merely consume without consideration for the human behind them.
2. Marketing Yourself
The other main reason we as artists choose to attend cons is to meet with the folks that can put us in touch with jobs. Art directors, game developers, publishers, etc. You'll probably never meet these awesome folks who lead you to professional opportunities unless you go to conventions! The downside, these folks may not be at smaller cons so you'll have to attend the larger ones which may not be local to you. True, you can still email in a portfolio, but I consider face to face interactions to be more memorable/powerful.
3. Meeting Kindred Spirits
After spending months in the quiet darkness of the art cave, getting out into the world again and talking to people who are just as geeky and passionate as you are can be such a gift!
4. Valuable Selling and Setup Experience
Every artist needs this! You need to know the joys of being juried into a show, meeting the deadlines of setup and application, the proper way to set up your display, etc. Most of all, you need the ever-important skill of dealing with people. A lot of us spend a lot of time alone without knowing how to market ourselves with confidence. This is an especially handy skill for when you want to start showing your portfolio to the folks that can get you jobs opportunities beyond selling to your fanbase.
1. Selling Too Early
Notice how I didn't put 'Making Money' as one of the Pros of conventions? It's my belief that most people who try to sell at conventions (including myself!) start selling too early. True, it's good to start building a reputation, but if you start doing that before your art is at a professional level, you start building the wrong kind of reputation. Chances are if you start selling too early, you won't have an established artistic identity or direction to your artistic vision. People will get to know your art by the lower quality and lower prices we all have when we first start out as green, wide-eyed wanderers in this grand art world.
One might argue that fans enjoy seeing you grow as an artist. I'm sure they do, but wouldn't you rather impress people right out of the gate? Starting too early can also lead to demoralization when you aren't making the kind of sales to justify your expenses because everybody else is levels higher than you, skillwise. If you're not sure if you're ready, ask your friends or art professionals you know whether they think you are at the point you need to be to take the risks of selling...because there are a lot of risks and a very high chance of burning yourself out when money is involved!
Chances are that 99% of you are going to lose money when you first start selling at cons (especially if you start too early). If you're lucky, you'll break even. There are countless expenses involved, including, but not limited to, gas, hotel, travel, inventory, food, art show fees, table fees, etc. While most of these expenses are tax deductible, it can really put a dent in your wallet and leave you with a hollow sense of failure after all the effort you put in.
And we haven't even talked about the sleepless nights spent prepping your inventory, making travel arrangements, setting up displays, eating badly, descending deeper into the anti-social art cave due to all the prep work you have to do, breaking down displays...the list goes on and on and on and on.
3. Time Consuming Distractions
On top of the dangerous levels of demoralization, conventions have a way of sucking up our lives. By the time you're done with one convention it's time to start prepping work for the next one! It's all about sell, sell, selling and sometimes you get so fixated on selling that you forget to make new work. A year (or two) later, you might realize you have the exact same work you're showing to fans and art directors and you're not advancing, artistically, because you've spent all this time making a short term dime instead of preparing for long term opportunities, like that portfolio you keep ignoring so you can SELL, SELL, SELL at conventions.
Bottom line is you need to balance conventions with creating new relevant work for your portfolio or you might find yourself stuck in a fruitless loop of selling.
4. No More Fun Times
After a few cons of selling, you realize that you aren't able to go to all the late night parties or stalk all the Jack Sparrows for your photo album or Pin the Tail on the Anthro. You've got a table to man and unless you have backup, you're going to be stuck there for 80% of the con. You'll probably need to be there relatively early too. Some of us can handle partying AND selling, but that's a recipe for a health nightmare!
Worse yet, you stop having fun at cons, altogether, because they are nothing more than selling opportunities for you rather than a place to be passionate about what you love with other people. Sure, there's nothing wrong with making money, but attending only to sell can sometimes sap the soul out of the whole experience, especially if you don't sell well and end up demoralizing yourself instead. I would personally rather be in the studio painting something for my portfolio that I can be excited about rather than selling at a convention I'm not really interested in. (Which is the exact reason for my break away from conventions this year)