I don't know the full details of Canadian electrical code. I know they base of the NEC just like the US, as the 2 countries work towards having the same code, so I will assume things to be the same as here. So if someone is replacing a panel, they will have to bring that part up to code as best as possible. Mainly this might just mean adding AFCI breakers to all the 120V stuff. Some cost associated with it might be that depending on the old panel setup.
In American dollars.
New residential panel $120
Guessing on breakers, and going for a worst case, with guesses of a typical house
Double pull breakers, qty 4 * $10 = 40
AFCI-GFCI dual function breakers, qty 20 * $45 = $900 max,
If they can just use standard breakers 20* $5 = $100
I'm going to assume there is at least 1 or 2 GFCIs in there now, so probably more like $200 min.
New SER cable from meter base (likely needed and with meter pulled for panel swap, why not) so 10ft * $5 = $50
So ~1110 dollars max for parts, or $410 on the low end.
It's going to be an all day job, between waiting on utility to come and pull power, then come back. Farting around pulling it, doing the job, I'd say full 8hr job. So 8hr * $100bucks, so $800 labor.
So I would expect something in the $1200-2000 USD $1536-$2560. Plus permits which were 600. -> $2136-3160.
So yeah, I would say those prices are inline. If you are used to the kind of work, then doing it yourself will save a bunch of money for sure. But you aren't going to avoid a permit on something like a panel, since you need the utility to come out. Not that anyone should be avoiding permits.
Like others, I will stand with the panel needs to go. But if you want to keep it, yet are struggling to find breakers, there has been a national shortage of them due to covid. Plants got shut down, many brands are made all in the same place. You might get lucky and they have a pile of them, or the one you need just doesn't exist anyplace.