I've rarely applied to anything with fees though I have on occasion paid a participation fee when the project is unfunded, whcih I think is fair enough and am happy to do that. But I have seen friends pay out large sums and then get the standard "sorry we had too many applicants" letter. I just don't recommend this - you are throwing money down the toilet.
I think that application fees have their place in certain cases, but it should be clear what you are getting for that fee. And it's interesting how suddenly everyone is doing it, like they figured out there is money to be made. I for one am not willing to pay a fee so someone just out of art school or "curating college" assesses my work, but I might do if it was someone well known and well respected.
I don't think it's right that a "curator" make money from fees. If they are talented they should be able to sell the work and so get paid from that, or attract a good commission. Surely they must teach them that in these "curating colleges."
Currently running an unfunded artist-run space, we decided not to charge for submissions but only ask participants to contribute to the running costs. So far we're only working with people we know but I hope this system can work.