Dollar wise, 2016 actually looked okay, until I added the cost of the booth that wasn't used, and then also, me buying things at a convention. The first image is me looking okay on paper.
This second image is me looking like a money tanking problem.
So, what happened?
At the end of the 2015 convention anyone with a table or booth has access to sign up early and save money on the next year's con. It's a tough choice every year, but we decided to do it again. It is a very fun time, and some of us make a little dough doing it.
Over the course of the year, life happens, and we lost 2/3rds of our table mates. Because I'm the one sort of pushing things, I tried and failed to fill the spaces. So I chose to eat the cost. I didn't really tell anybody. Which is foolish on my part. But understand that I view the convention as a freaky vacation, and that money kind of gets ear tagged as stuff I might have spent on another sort of vacation or xmas presents anyway. Also understand that a big reason I do conventions is to force myself into interactions with people. I have huge anxiety about this, lots of people do. So filling those spaces, feeling like I'm begging or intruding, was difficult just to try. I spent too long before asking for help, and then the con was on. So my 300 or so table was now 5 times higher. Ouch.
The biggest upside this year was that I spent way way less on making the sketchbooks. I thought that would put me in the good zone in and of itself. While that didn't happen, I'm extra glad I didn't spend money on a nice cover again.
Then I spent money. Money on some normal things like eating and parking. Money on comics and artwork to support other artists. Buying directly from the creators instead of the book booths that also had their books. Trying to buy from artists I like and trying to spend it on original content instead of fan works, because I want to see new ideas and worlds being born in unique styles. It is really really hard not to buy fan art at a convention. Try it sometime. When you love an IP and someone made something really unusual and fun with it, and spent a lot of time and care, it's so hard not to bite.
Another thing that happened over the last few years... When conventions get very large, over 50k people I'd guess. Selling becomes exaggerated very quickly. You end up with feast or famine situations. The saturation of good content, the pressure of the crowd, and the extended hours begin to hit everybody. So you end up with a growing number people losing money(people a lot smarter than me financially), a group that gets pressured really hard to produce fan art along with their original works just to keep up, and a small number of people selling gangbusters, which seems to be large vendors on the whole.
My two cents on actually making money.
Mostly sell at local conventions to keep down costs.
Don't make books unless someone else paid to print them.
Prints are great, but most people want art in color, not black and white.
Don't make large posters, keep prints small.
Everyone is selling books and prints, if you can make something unusual and remotely useful it should do well.
Little pinback buttons are pretty great as far as cost effectiveness goes.
Make sure art is at three levels, waist, shoulder, and head(or higher).
Get a folding hand cart.
And, sigh, make some fan art, just make sure you add value to it so it's unique and new.
For most people, money isn't going to make running a table or booth worth it. So make a point to understand what the value is to you beyond that. What do you want that experience to be.
Personal growth? Parties? Professional connections? Trial runs?