Is it cheaper to buy the split systems ourselves?

So I'm looking to get some multi head split systems for my new house. I was wondering if it would be cheaper to buy the split systems myself (both indoor and outdoor unit) and just hire the trades to do the installation or should I just let them handle both the supply and installation? TIA.

Edit: I got a quote of 13.7k total for 1x7.8kw unit and 5x2.5kw units Mitsubishi electric. Just wondering if that's reasonable or not.