Gunite Pool Depth versus Cost

I have met with a few well known gunite/shotcrete pool companies to construct a new free form 1000 sf concrete/plaster pool plus 8 foot spa with natural boulder waterfall in Putnam County, NY. Proposals have ranged from 75,000 to 100,000. My original thought was to go with standard slope from 3.5' to 8' but after a lot of discussion we will not allow diving due to insurance/safety reasons. Our family prefers mainly water sports where everyone can stand (volleyball, basketball, etc) so we decided on more of a constant depth pool ranging from 3.5' to 5.5 feet. I was surprised that the contractors told me that this change would have minimal effect in reducing the construction cost. Can someone comment on whether this makes sense or should I push back and if so by how much?

thank in advance