The problem with pay across the board reaching 80 is that (unless there's zero pay increases and the TOC average from the link below is accurate in numbers of guards) there's just not enough guards (about 16% of staff) on the network to get from 105 to 80 in pay costs.
Also given that the pay of guards is (again on that link below) is ranked 30/45 (£33,171) there's plenty of staff payed more (many above guards are much smaller numbers of staff), including about the 30% of all staff who are train drivers (£58,120), which further reduces the ability of the government to get enough of a pay cost reduction to reach that level. I suspect that even a fall of 10 would be hard-pressed to be achieved, even if there were zero guards on the network.
https://www.google.com/url?q=https:...QQFnoECAMQAg&usg=AOvVaw1rkBQBB90RIzYi-OgrqsRg
However if you get rid of guards you then risk increasing ticketless travel (and so reduce your income) so to counter that you then need to have more gate lines and staff at stations to reduce the losses.
Whilst gate line staff are payed less, the goal of getting rid of guards is to significantly reduce your costs. However to make any meaningful cuts you've got to not replace the guards with another member of staff.
Having dug into the numbers a bit more guards basic pay is 13% of the total of total basic pay and whilst there would be a few other roles which could be reduced, to totally do away with all second (safety) staff members (i.e. there could be catering staff) would likely save you 15% of your basic pay costs.
However if you had employ 10% of the number of guards as gate line staff (the average TOC employs 7,000 guards, so this would mean employing an extra 700 gate line staff) that would reduce your savings from 15% to 14%.
However given that you need at least 3 staff to cover 1 station (early, late and weekends/holidays) with one member of staff on duty from first to last service, as well as quite a few stations needing extra cover, you're likely to end up with a significant number of extra staff very quickly.
Whilst some may then mean that the ticket office staff are moved to gate line duty (where you could also buy tickets), there's also going to be stations with 2+ access points, which then means either having remote operating gates or extra staff (or a combination of the two), unless you close access points (which would put people off using the railways and reduce your income).
The final point, is that (using SWR as an example) passengers like the fact that they know there is a member of staff that they can talk to if needed and to do away with them entirely could put off a lot of people from travelling - especially late night. Whilst late night travel is fairly small, if you can't rely on that you may find that you justify the need for a car and so remove quite a lot of rail travel.
Overall the cost savings compared to the risk to revenue is likely to be limited.
Whilst first to last staffing of stations makes sense for high frequency services, for lines with limited frequency where there's a decent amount of travel between stations which aren't overly large and those larger stations would need more staff to run the gates to first/last services then the removal of guards could actually be more costly than retaining them.
That's all assuming that the train drivers don't require more money, as for every 1% more they require for DOO that's 3% of the total cost of the guards pay. This could mean that rather than a 15% saving, if the drivers required an extra 2.5% the saving would fall to 14%.
Likewise (assuming the 1/3 lease, 1/3 staff and 1/3 other for costs) a 0.5% fall in income through ticketless travel would erode a further 1% of that 15% of savings.
The need to employ 20% of the number of guards, a 5% pay rise to drivers and a 2% fall in revenue (loss of confidence to travel by train, more ticketless travel, etc.) could mean a 15% pay saving becomes 7%. Obviously it could be better than that, however it could also be worse.
Although given the old ratios of 1/3 being staff costs, even at 15% the total saving would be 5% if we could get rid of guards entirely without there being a need for more other staff, paying the drivers more or reduction in income. Factor those in and it's possibly about a 2% saving. Whilst not to be sniffed at, it's not going to reduce the over value of support to the railways by very much (pre Covid, it could have reduced it from £7bn to £6.5bn, during Covid the reduction would have still been £0.5bn but the level of support was much higher).