Talking hypothetically, they may have an amount of capital that they have / can borrow, but it has to equate to the actual build cost of any stadium.I'm very confident we would not be this far along the process if Mr Moshiri (& his mate) did not have the funding sorted.
They even back heeled the offer from the council , this suggests to me they already have this in hand maybe at better rates.
What you can get for the ballpark figure of £500m (I expect it'll be closer to the £400m mark) depends on a variety of factors - building on a dock being one.
Personally, I'd hazard a guess that rising costs compared to the amount of capital we can spend is a reason for lower capacity and scaling back of plans...
... rather than an actual lack of ambition. Unfortunately, we're not a club that can go out and spend huge sums like other clubs could perhaps do.