Whilst it may seem the use of local tradies would be cheaper, they may likely fail to meet the criteria of the Strata manager in terms if insurance, workers comp etc, and they therefore would take no responsibility for any failure in the work of the contractor you chose. You would have to follow up the deficiencies and not the Strata manager.
I do agree Strata work is a cash cow for the big companies and they charge like wounded bulls.
High levies, as people have said, could be a failure of a committee to build up sufficient reserves in the capital works fund.
Look at your building’s 10 year plan. That may clue you in the works down the road and you are building up reserves to meet that.