Upgrade Miles (and tax????) Question

Evening Everyone,
Just had a weird conversation with CS when booking some flights yesterday and just wanted to run it past everyone.
I have booked M class Economy previously and used miles to upgrade, I have also had an M class and just used miles to upgrade at the airport....
Yesterday, I noticed reward seat availibility for 3 G's (amazing I know, been watching 3 times a day since the 1st of January and noticed more errors with the website in the process which i'll explain later)for the LHR-DXB route for March. I called up and asked for 3x M class Outbound and I asked for O class return. This is so i can just upgrade the outbound. The CS agent said the price would be 20,000 miles per seat including the differnece in tax between economy and Upper. This confused me, surely it's just the price of the M and O return plus the miles. Obviously I really have no way of checking online as the web will not let me check mixed classes. I queried what she said and I was replied to in a .... it's been like that for the 12 years i've been here sir tone. Am i missing something?
It just feels like if i had just booked the M and O return and not done the Upgrade at the time, then it might have been cheaper?
On the spotting the website not really working again!!!! I would check the availibility calandar by doing a dummy rewards booking and say the 4th would appear, then call CS only to be told it's not there. I understand I may have just missed it as the web lags behind the actual booking system. But as i'm watching it like a hawk... 4hrs later two dates magically appear... again i call only to be told... there is no availibility. Repeat this every day for 20 days pretty much. Just seemed to be the month of March on the DXB route. A very helpful agent in Swansea actually penned an enquiry to IT while i was on the phone to them one day. Even the days she coud see on the system apparently were not there either. Seems fixed now
Just had a weird conversation with CS when booking some flights yesterday and just wanted to run it past everyone.
I have booked M class Economy previously and used miles to upgrade, I have also had an M class and just used miles to upgrade at the airport....
Yesterday, I noticed reward seat availibility for 3 G's (amazing I know, been watching 3 times a day since the 1st of January and noticed more errors with the website in the process which i'll explain later)for the LHR-DXB route for March. I called up and asked for 3x M class Outbound and I asked for O class return. This is so i can just upgrade the outbound. The CS agent said the price would be 20,000 miles per seat including the differnece in tax between economy and Upper. This confused me, surely it's just the price of the M and O return plus the miles. Obviously I really have no way of checking online as the web will not let me check mixed classes. I queried what she said and I was replied to in a .... it's been like that for the 12 years i've been here sir tone. Am i missing something?
It just feels like if i had just booked the M and O return and not done the Upgrade at the time, then it might have been cheaper?
On the spotting the website not really working again!!!! I would check the availibility calandar by doing a dummy rewards booking and say the 4th would appear, then call CS only to be told it's not there. I understand I may have just missed it as the web lags behind the actual booking system. But as i'm watching it like a hawk... 4hrs later two dates magically appear... again i call only to be told... there is no availibility. Repeat this every day for 20 days pretty much. Just seemed to be the month of March on the DXB route. A very helpful agent in Swansea actually penned an enquiry to IT while i was on the phone to them one day. Even the days she coud see on the system apparently were not there either. Seems fixed now
