Agencies do not normally insist you pay exorbitant...

Agencies do not normally insist you pay exorbitant rates to see only Thur photographer, attend their workshops, etc. The standard practice is for an agency to take a percentage of your pay. Anything above and beyond is a scam. Considering their only response to this knowledge being shared is, "we've been around a while. We can't be a scam or unethical!" You can see what type of place they are.