No really, excellent reputable breeders doing it properly, are not making a profit out of it.
In addition to what adaline has posted..
Travelling the country showing or working your dogs, or seeing other dogs shown or worked - costs a bomb. A single entry into a champ show is £23, plus your food and fuel for the day, plus that is a day you aren't working and many are thurs/friday/sat/sun, it isn't just weekends...
Time off whilst you actually have the litter - lets say both of you have 3 weeks off work and you pay someone to cover a couple of weeks because you cannot go and leave a litter of puppies 8 9 hours whilst you work. This tends to be unpaid leave, or a period where a self employed person just doesn't earn.
The costs of keeping dogs, insurance, food, vets, running on pups to see if they are the right quality then rehoming or selling on at a reduced price when they are older if it turns out they are not.
You also need a slush fund, around 3 to 5K on hand because whelping emergencies are not covered by any insurance, you need a middle of hte night bank holiday emergency c-section doing, you fund that up front yourself.
If you aren't doing the above, arent travelling, working, showing your dogs and seeing other peoples dogs out and about, you aren't doing it right because you don't know that you are breeding the best to the best, you've no idea how your dogs stack up against anyone elses.
So yeah, good breeders don't make a profit, they MIGHT break even in the short term, but long term, they are not even covering their own costs - its something they do because they are passionate about their breed, NOT for money.