But thats not true at all.
If you start at 18k then decide to build on, then you have 2x design, commissioning, certifications, the cost per m2 will be higher as its a much smaller manufacturing job & more bespoke- I'd say £4m. Build 24k from day one and the overall cost is much less, payback period on those extra seats is much shorter, and you're well equipped for the future without having to potentially choose between 2 new players or more seats at some stage. And your logic on crowds is nuts.
To be honest this is really basic stuff, costing this up I mean- and it just makes me think that its bullshit. I want it to happen, and the partnership makes a lot of sense, but the actual nuts & bolts of the ground itself- it reeks of someone making it up as they go along and throwing buzzwords like "expansion"/ "modular" around. Nobody would do it this way if they are all about costs & forward planning. As for "expansion"- how many clubs have you seen expand their grounds, even though there is a patent requirement? Liverpool is one, we're hardly Liverpool, Stoke did but it took years to bite the bullet. What makes us think that we'll start adding a few blocks of seats every time we have a good season then ripping them out if we go down?
I'm telling you- this view that "oh its ok, if we need them we'll throw up 5,000 more seats, no bother"- it doesn't work in reality, sounds great but it doesn't make any sense at all for us, practically or financially.
Therefore you're looking for a ground that makes sense and does not force you to budget for an expansion which you could have had on day one for lower cost, and which would have made sense anyway, so 18k (or 15k home seats) is bullshit, it really is.