Amarr is the second largest trade hub and while it is a long way behind Jita, it’s still a fair bit in front of the others.
So yes, you’ll have more competition, but also more buyers and the velocity of your ISK through Amarr will be faster than in other trade hubs (including Dodixie in general).
How fast your ISK moves is just as important as your final selling price.
For example, if you can sell 1 of something for a 20 million ISK profit in Dodixie per day, but can sell 3 of them at 10 million profit each per day in Amarr, then you still make more profit by selling in Amarr, just because your ISK moves faster by the goods selling at higher volumes.
So it’s not all about price. It’s also about how long it takes to sell things and the more you can turn over your ISK, the more profit you can make in the same period of time, even if you are making less profit per item.
Those figures above were just plucked from thin air. They aren’t the real margins, so you’d need to check that first.