Looking at our fees page, I believe we can be clearer about disclosing how we calculate the exchange rate for Bitcoin Deposits and Withdrawals. I've brought this up with our team and I think there will be changes made shortly. We will soon be listing the real-time buy and sell prices with our spread factored in.
Essentially, our spreads on both sides is 2.00% over our own wholesale buy and sell costs, which itself can vary compared to the global BBB that you linked to. While the price is stable, that spread shrinks, and it grows when the price is volatile. Currently the difference between the buy and sell prices is about 5.5%, we like to have that closer to 5.0% which is exactly in line with our foreign currency exchange rates (2.500% on either side, buy or sell).
It's important to note that Payza is not a traditional Bitcoin exchange, our service is more in line with traditional currency conversion. The vast majority of our members use Payza for much more than Bitcoin exchanges, and this service acts as an introduction to Bitcoin for our interested members. We have attracted new members that have a greater interest in Bitcoin since adding this feature, but admittedly, for early adopters and savvy Bitcoin users who are more concerned with getting the best rates, Payza may not be for them.