Upgrade online with money after booking

Maybe it's because I haven't had to book flights directly with VS other than on LR for a while (my last flights with VS were on red vouchers, and 2 work bookings including one via DL).

So after I booked the flights to GND in Jan (outgoing in O in EC and back in K in PE) , I noticed that in my "future bookings" online, there's an option underneath "choose seats" that allow me to upgrade with money now, indicating how much it would cost (for the outbound it allows me to upgrade to PE and to UC). When I first booked (during the last sale), I checked the prices and it would work out the same as paying for the higher class to start with. Recently for the return trip, the "upgrade to UC" (from PE) option has disappeared, probably due to limited availability.

I think this was the first time I came across this option online -- is it often available? The reason I ask is that if this is available, then potentially I'll be able to upgrade myself on a work trip with my own money, if desired. My previous understanding was that upgrading from an fare code that's ineligible for upgrade (both O and K in my case) would usually cost a lot more than the figures I'm seeing.

Have you seen this before? or used it?

Thank you guys.

AFAIK, the O and W fares are non upgradeable "when using miles," they're still happy to take your cash otherwise

However, they've offered me cash upgrades on the site before exactly like this and I have taken them up on it. Typically, it's either close to the difference in fare (O -> K, for instance) or around the price of an at-airport upgrade. Both times I've done it, the price has been very reasonable.

I've been unable to determine why it happens so I've chalked it up to changing availability and fares.

It will also only be an available option if you have booked direct with VS - you can't upgrade travel agent bookings this way.

It will also only be an available option if you have booked direct with VS - you can't upgrade travel agent bookings this way.

Ah I see. I guess I wouldn't have the easy option of upgrading online if I wanted to. Do you think I can call VS prior to departure to get an upgrade price or to ask at check-in? I suppose it wouldn't hurt

on flights booked by my company's travel agent VS always refuse to do any upgrade in advance, i'm AU often with umpteen points but they stick to the rules, i've tried begging, that didn't work either

but at check-in they get flexible