It's the old sweetspot economics argument. For each 10k increase in capacity, the overall cost can increase by 50% or more, as heavier structure, more vertical transport, more floors/floorspace, more roof area etc are all required. Yes, if it's a freeby stadium, or if your owner has really deep pockets, they can afford to "stack 'em high and sell'em cheap". However, if the club needs to cover the costs or the owner wants a short term ROI, with new seats that pay for themselves asap, then they'll want to control those costs and at a capacity that maintains a healthy demand, that won't require selling cheap ticket prices to fill it. We don't yet know how solid or cost resilient our waiting list is. It has grown out of years reasonably priced season tickets at a limited capacity stadium. Opening up that capacity too far and having to increase those ticket prices to cover the subsequent increased costs, could see those waiting lists disappear. After all, 53k represents a not insignificant 30% increase in capacity.