A group buy takes time and effort from a single person to see from beginning to end. It is not their full time paying job, in fact, they don’t get “paid” for it at all, and they do it in their own spare time, outside of also a job elsewhere
The additional costs compared to buying direct for the item itself are a fee that represents the fact that someone else is doing the leg work for you, plus a contribution to the platform upon which you were able to secure a copy without hassles and disappointments from going direct. Think of it as a form of priority compared to joining the public queue to get one, and that benefit doesn’t come for “free”
As for the shipping, Manta releases (someone can correct if I’m wrong) are shipped to a hub from Manta, and then forwarded on. Therefore Manta charge to ship to the hub, then the host or person shipping it in to you, will also incur shipping fees. Therefore the shipping is also higher due to the multiple shipping points and trips instead of direct
If you personally feel it is a scam, then don’t buy through a GB, simple. You’re not forced to, nor coerced to either. Go direct if you want to avoid these additional fees and good luck to you