It is really, REALLY, not that hard to diagnose fish.  You just have to read voraciously about it for a month or so and know what to look for and where to pay close attention to symptoms that may seem the same but really aren't (ich vs epistlyis for example).  

If you can't be bothered to learn then sure you can shell out for ridiculous vet bills, but you don't need to and shouldn't feel bad for not doing thay.

But, in my experience, anyone in this hobby who sticks with it long term is here because they have a genuine love for ichtyology and can't get enough of the learning part.