That's £9,381 if priority processing is used at each eligible step, and assuming the fees will remain frozen. (priority, not super priority which is £800 as opposed to £500 extra)
I believe the priority and super priority services have returned to select locations following previous suspension due to the pandemic?
The regular priority service is not available to FLR(M) or ILR (SET(M)) applicants (see here:
https://www.gov.uk/faster-decision-visa-settlement/eligible-visas-when-applying-inside-the-uk - the table shows that the 5-day £500 service is only available for student and work visa applications).
So, the only option for faster processing for FLR(M) and ILR is the £800 Super Priority service.
So, the actual fees are (at current prices), with all the expedited processing services, plus mandatory extra biometrics fees and IHS surcharges
Initial fiance(e) visa = £1,523 + £573 priority processing = £2,096
First FLR(M) = £1,033 + £800 Super Priority + £1,560 IHS surcharge + £19.20 biometrics + approx £135 biometrics appointment fee = £3,547.20
Second FLR(M) = £1,033 + £800 Super Priority + £1,560 IHS surcharge + £19.20 biometrics + approx £135 biometrics appointment fee= £3,547.20
ILR = £2,389 + £800 Super Priority + £19.20 biometrics + approx £135 biometrics appointment fee = £3,343.20
UK citizenship application = £1330 + £19.20 biometrics + approx £135 biometrics appointment fee + £80 ceremony fee + £75.50 passport application = £1639.70
Total for everything = £14,173.30
Or if you were to marry in the US and apply directly for the spousal visa, the fees (including expedited services) would be:
Initial spousal visa = £1,523 + £573 priority processing + £1,872 IHS surcharge = £3,968
FLR(M) = £1,033 + £800 Super Priority + £1,560 IHS surcharge + £19.20 biometrics + approx £135 biometrics appointment fee = £3,547.20
ILR = £2,389 + £800 Super Priority + £19.20 biometrics + approx £135 biometrics appointment fee = £3,343.20
UK citizenship application = £1330 + £19.20 biometrics + approx £135 biometrics appointment fee + £80 ceremony fee + £75.50 passport application = £1639.70
Total for everything = £12,498.10
Note: there are supposed to be free biometrics appointments available but they are difficult to get so most people applying in the last year have had to pay for them and they are anywhere from about £75 to £140 per appointment.