The Deloitte figures are a bit out of date as based on older prices but they provide a fair benchmark.
You can work out roughly from prior year match day revenue, season ticket sales and quoted attendances how much we take per game for different groups of ticket e.g. Full price/early bird/ discounted adult season and single ticket, junior equivalents etc. Considerably more than half our ticket sales are at a substantial (20% minimum and for juniors/infants far more) discount to a single adult ticket price. I estimate this season our average per match take per fan will be nearer £25 than £30 including retail profits.
If you extrapolate this then a 7000-8000 attendance increase adds about £6m to revenue if you assume a significant proportion of increase is from boxes, exec/lounge seats etc. and a "fair pricing" policy to avoid price increases and maintain or even extend discounted options. Effectively the average take per new seat is assumed to be £40 factoring this all in.
Several PL teams in London significantly exceed £50 per fan meaning a 40k crowd for them would require us to sell >70k to match the revenue even in a new stadium assuming we get towards £30 per fan average.
The direct benefit of 10k extra capacity is marginal at best for us and still leaves us massively disadvantaged vs. London clubs and our Northern rivals with massive global fan bases and fly-in fans. If we are lucky we cover increased costs and interest/debt repayments with direct match day revenue.
So, this has to work on a second level by improving overall perception and visibility of the club to boost attractiveness to commercial partners and generate indirect revenue benefits. It does eliminate a key negative for a potential buyer/investor (it does not create a real positive differentiator unless it draws in hordes of new, largely overseas fans, by coinciding with playing success).
We do need better facilities and increased capacity but we must be realistic about the benefits.
(Before anyone asks, yes I am a qualified accountant and business executive so sorry about the numbers and realism!)