(MEL) Retrofit of inverter AC system

Looking at getting ducted inverter AC system installed in our house we've just bought and moved into. It is a gorgeous 1950's cavity brick house, but needs AC (already has gas central heat under floor).

I've reached out to a group of installers, and the first one to come back to me was a bit of a shock, but I really don't know what to expect in terms of price either.

It's a 3 bedroom, 240sqm single story house. Our request was for linear grill vents, some kind of zoning capability, outlets/zoned per bedroom, and then living areas (2 living rooms, and a kitchen and an entrance way) as a combined zone.

The first respondent was insistent on Mitsubishi Electric PEA-RP140GAA - i've got no real idea or expert on systems so i'll just accept this for now. Upgrading with WiFi controllers on top of the zoning and linear outlets, the install price comes to approximately $17k.

This price was a bit of a shock - but I don't really know what to expect.

Can anyone please comment on retro fits to existing houses on 4 zone ducted AC prices or if this unit is any good or not?