Horrible Hydarulics Again

Our Hydraulics plan was sent to Wisdom by the engineer approx a week or 2 before they lodged our plans with council. We never got to see it until a week after they lodged the plans, so too bad if we wanted anything changed. We asked many times for a copy. We also consistently asked for the variation on the cost of the hydraulics.  We finally got that 4 weeks after they lodged with council so too bad if we weren't happy with it. Our CSO at Wisdom was considerate enough to call before she emailed the variation to me, so she could give me the bad news over the phone on a Friday evening just before their office closed. It was double what we were expecting. Their sales person only advised us to put a $5000 provision in our tender for additional hydraulics. The variation was $24000. How wrong could they be. I asked her to email it to my husband as well as I didn't want to be the one that told him and then be in his firing line.  So for some unknown reason it took them 6 weeks to get me a quote for the hydraulics, and now they have pretty much taken any chance we had of reducing the cost by coming up with an alternative, away from us. They blamed the plumber for taking too long to provide his quote. Since we are in council, if we change the plans it will cost us in engineer and council fees, not to mention the delay. We have already been charged once to extend our tender.
My husband had the weekend to regain his composure and then called Wisdom on the Monday. We asked for a breakdown of the costs for the Atlantis system underground stormwater pit. Everything else was itemised except that and we know all the components required to construct it, so we just wanted to know why it was such a costly item.  They refused. My husband asked what would happen if we refused to sign. They said they would end the contract with us. It has taken us 2 years to get to this point so that idea didn't thrill us.
So here we are over a barrel. Not loving Wisdom too much at the moment.

Our OSD calculations and plans are shown below.