The BT Wholesale Carrier Price List
here gives prices that it charges other telcos to terminate calls to its NGNs or transit to other terminating providers.
See
section B1.06:
Quote:1.6.4 National Call™ 0870 (other than BT Click™) Calls
Description | Effective Date | Until | Daytime | Evening | Weekend |
All Operators | 01/10/2006 | 31/03/2007 | 5.9100 | 3.7000 | 1.7441 |
All Operators | 01/04/2007 | | 5.8229 | 3.5082 | 1.6116 |
If I've understood it correctly, then BT makes a loss on these numbers during the evening and weekend. Remember that the retail prices must be compared without VAT, and not with as we commonly think of them. The loss shows how much they make from them during the weekday daytime.