To be clear, I don't think they're doing it this way BECAUSE (or mostly because) it's cheaper, but that it's easier to organize in volumes/priority that people want.
My guess is that the blockage is not so much money, but that they would have to radically change the planning and processes for the in-person ceremonies (compared to the pre-pandemic scheduling for in-person, which I think is at core of how their system works now). There's no reason the rescheduling as they have it now should take so long, for example.
Or put differently: I think they'd have to rip apart the two-track system now and re-build it, using the lessons from the pandemic and all; and they just don't have the bandwidth / prioritization (unless a minister or the public demands it). It wouldn't have to be all that expensive necessarily - just different.
For example: they could issue everyone who gets all the approvals (ready for oath) a number they can use to get in to a ceremony and a 'default' ceremony online six to eight weeks away. Then they set up regular large ceremonies in population centres (Toronto/Montreal/Calgary/Vancouver could probably have every day, or several a week, or run five or six one day a week). If it's 100-200 per ceremony, 80% of them reserved in advance, 20% 'day of' (be there an hour in advance to register and show your ID etc.) Rent a theatre in Toronto and do 600 people at a time, once a week - whatever. Make it regular and a mass event.
anyway, not going to happen unless a lot of people tell the government they want it (and even then probably not right away)