You can't really compare testing fees or duration without understanding what goes into them. For example, my system's black belt test costs about $100; $50 for the test and $50 for the camp. That doesn't include getting CPR certification, travel to the campsite, and so on. The PT test phase takes several hours; the skills testing can take a few more hours. Is the fee reasonable? Is the duration fair? Others have taken tests where the PT test alone is an entire weekend -- with another weekend dedicated to skills tests. Some have paid nothing for tests; others have paid thousands.
You have to decide if the costs and time are worth it TO YOU. The cost and duration have nothing to do with whether or not YOUR skill is real. Or your rank truly earned...
However -- I'm not suggesting that any testing fee is reasonable, either. To me, the red flag is the combination of lots of testing fees, with little explanation, or having tests simply to add up the testing fees. Proliferating belts (with accompanying testing fees), and so on, where there's always "one more fee" is a sign of a possible scam... Just like it would be in anything else.