
These Ukrainian based companies charge more because they work on the premise that "you pay for quality".
If you find a writer that works well for your writing needs, you will want to hold on to that writer. Which is why the company charges the client more. From my experience though, the increased rate does not include an actual raise for the writer assigned. The writers do no have any idea that an increased rate is being charged because they are paid the same rate by the company.
The only benefit of being a preferred writer for the company is that the writer no longer has to bid on work orders. The automatic assignments come as a blessing to most of the writers because it offers them an increased income for that pay schedule, in addition to the regular bidding work that they do. Technically, you should not have to pay extra for the service and if I were you, I would not go with a "preferred" writer at the company. As a word of caution, I have to inform you that these companies may not even assign the paper to your preferred writer.
There were instances when I was told by my regular clients that the company said I was unavailable to work for them, which wasn't true, but they were encouraged to pay the "preferred" writer rates as the order would be assigned automatically, as soon as I became available. I never did get those assignments for some reason. Don't pay more, just pay regular rates.
It's better for your pocketbook and the writer you want will most likely see your order and bid on it anyway. In which case, they assign the paper to him / her just the same.