notime

There is not one rate for all countries.

Each country has various different consumer rates with a maximum per minute. Each country has different VAT percentages included in those consumer rates.
Next to that, the payouts vary per consumer rate AND per mobile/land line operator/network also.

The phonebilling companies get additional payouts from their suppliers based on volumes they do monthly, some phone billing companies pass that on to their clients in their payouts.
Then they also need to take the currency exchange rates into consideration since some networks payout per month, some per 30 days end of month.
With various currencies and a consolidated payout to clients, I guess they have (and need) a small margin to cover the possible flux in those rates.
Some countries may have a monthly fixed fee to obtain a dedicated phone number for this kind of service. This is not something the phone billing companies get for free.

For example:
I use www.dialxs.com for my VOD in Holland and Belgium.
Say I want to charge 8 Euro to a user for a video to download. The max. consumer phonerate in Holland is 0,80 euro per minute (INCL. 19% VAT). Then the consumer calls a number, stays online 10 minutes (8 euro devided by 0,80 per minute), the line auto disconnects and sends a signal back the product has been paid for.
The payout would be 0,515 EX 19% VAT (or more if you do real volumes). Times 10 minutes that would be 5,15 Euro EX VAT (which equals 6,13 INCL VAT). So when the consumer paid 8 euros and the nett is 6,13 (both incl. vat), the payout is around 77% of what the consumer paid.

But in Belgium and Germany you can bill 2 euros per minute, just to point out the difference.

Hope this helps.