According to
ORR Rail industry finance (UK) data portal total rolling stock charges have been increasing year on year due to the new trains being introduced. They don't cite the 701's but in the commentary for last financial year they note the following train operators had the largest increase in costs:
(a) London North Eastern Railway costs increased by £129 million (63.0%) to £333 million due to the introduction of new Azuma trains;
(b) East Midlands Railway costs increase by £14 million (28.8%) to £63 million due to the introduction of the Class 170 Turbostar and Class 360 trains;
(c) TransPennine Express costs increased by £27 million (22.9%) to £146 million due to the introduction of new Mark 5 vehicles
The 701 capital cost was quoted as £900m the book value of the 455's is nothing like this albeit their value would have been increased following retractioning. This was all factored into the First SWR bid and i suspect they thought they would get DOO in with new stock but we know whats happened to that.
Anyhow there ought to an enquiry into whats happening with new rolling stock currently. This isn't the only fleet thats not being put into use for the benefit of the passengers who are indirectly paying for them through the farebox and the tax payer who will be on the hook to support the industry to the tune of billions per year for sometime yet.