Both bridges are the same price. They are owned by Severn Crossings PLC and [alledgedly] when the owners (partly french) have recouped their outlay on the cost of building the second bridge + a profit, the bridges will revert to public ownership (i bet the cost to cross will go up).
I grew up by the bridge (as was) and when the prices suddenly shot up, it really ripped up the area, lots of folk who lived in chepstow and the wye valley worked and had family in bristol + vice versa; it never recovered from that. The evasion going into wales is massive via the A48, A449 etc.
The welsh assembly hate it, as companies do not like investing in south wales due to it.
Incidentally the reason that charges are made going into wales, is to prevent traffic queuing from the old toll plaze onto the old bridge (as used to happen all of the time) as the old bridge is pretty poorly with extensive corrosion on the interior of the deck sections and to the cabling.
