I don't think you've proven your theory. It's not for me to disprove your out there theory that Hulu is worth 20-25B because it has 1/6 the customer base of Netflix. You use a lot of ifs and assumptions there, whereas I'm using actual data. I want to add that the burden of proof is on you.
People can say all kinds of weird theories, it's not up to me or anyone else to disprove it. Six Flags and Cedar Fair have ~1/5 the attendance of Disney, then they should be worth 1/5 of 150B that is equal to 30B, but they are worth 5.8B and 2.95B respectively. Your theory makes no sense, especially when we have data backing up the 8-11B valuation.
Six Flags and Cedar Fair are only comparable to one aspect of Disney's business (which accounts for somewhere around a third of its revenue and profits), and all 3 are public companies.
I could use Six Flags and Cedar Fair to provide valuation estimates for Disney or Universal's theme park business by comparing their relative attendances and ARPUs to divide the latter two from their parent companies.
We could look at Disney that has 5x the attendance of those 2 and generates at least 2-2.5x the ARPU and end up with a valuation for Disney parks somewhere around $50-70 billion (and you'd be right).
Netflix is a public streaming company whose non-streaming businesses are negligible in terms of earnings and they have 130 million subscribers of which the market applies a value of $160 billion to it. Netflix had $11 billion in 2017 revenue and $2 billion in negative cash flow. The market basically applies a relative value of $1200 per subscriber in the context of all of those numbers looking forward.
Hulu is nearly identical to Netflix in that it is also a streaming company whose non-streaming businesses are negligible in terms of earnings and they have 20 million subscribers. 2017 revenue for Hulu was around $2.4 billion (including $1+ billion in ad revenue as they publicly announced that), and Hulu had $920 million in negative cash flow.
Based on a valuation of $9 billion, Hulu would have a value around $450 per subscriber.
But Hulu generates more annual revenue per subscriber than Netflix: Hulu gets around $120 per subscriber whereas Netflix is at around $100 (currently).
The main reason Hulu is correctly valued less than Netflix is that Hulu is US-only and Netflix is available everywhere.
Okay let's untangle that: Netflix has 55 million US subscribers out of its total, and if we were to extract Netflix US from the whole company, we'd have to account for how much faster international is growing (even if less profitable per subscriber).
You probably end up fairly saying that Netflix US has 42% of current total subscribers, but in the future that will likely drop to around 25% over the next 10 years as international explodes. US subscribers are always going to be significantly more profitable (right now Netflix derives profit off US subscribers and losses on international).
Once international is profitable for Netflix, I can see Netflix deriving around 30-33% of its long-term profit from US streaming despite only having 25% of its subscribers in the US on a longer-term basis. Basically, 30-33% of its long-term $160 billion in value is coming from the US, which at the low end is $48 billion in market value from the $160 billion market capitalization.
Netflix's 55 million US subscribers is valued forward at $870 each.
Hulu's US subscriber base should be valued more than Netflix's because Hulu generates ad revenue off its subs (and Hulu is growing quicker in the US than Netflix which appears to be mostly tapped out).
So Hulu's $450 per subscriber valuation from the bankers is undervaluing it by 50% on a comparable market basis to how public markets value Netflix.
Either way, it's pretty clear that the market values Netflix much higher on a per subscriber basis than the various Hulu valuations that Disney/Fox and their bankers are using. You could say the market is too bullish on Netflix (I would agree). But at the same time, that's what a market price for Hulu would look like: somewhere around 2x what Disney's private bankers are telling it...
Of course, there might also be some gamesmanship here: Disney only owns 60% of the asset in question, so being extremely conservative in valuing it makes sense. You wouldn't expect Disney (or its bankers) to start telling everyone: hey this asset would be worth $18-20 billion if publicly traded, and we're looking to buy 40% of it...