Lol no offense, but if anyone asked for $10-$20k for an "addon" I would walk away ASAP.
You misunderstand the point completely...
The direction the thread was going, people suggested someone making and selling this as a solid product fully integrated into xf with a pretty rich feature set and for a professional familiar with MVC OOP who codes in php for a living, they can not put the effort and time it takes into the project for 1500 - 2000 and still make a living. The value of a product doesn't change if you pay more or less for it...that comes down to how it is marketed...in the end the cost to develop the product would remain the same regardless to if it was sold to one person..a limited group of 5 people or available publicly all at different prices...the programmer would obviously be trying to target a number no matter how they sold it...if they sold the rights to it completely they have to calculate the potential of what it will earn right now + what it can earn lets say over the course of 5 or 10 years before they could negotiate a price for the sale of it to someone who can market it properly.
I myself have made a automated front page replacement system built on top of the WFw which replaces a blog or another front page system and it does the job pretty damn well too and I did it for what equaled out to about the amount in the thread title suggests if you factor in that I did other things as well for one total price when applying this to their site. However I also customized it for their needs and it was done in a way that is not a simple one or two click install so it is not a product that is ready for a marketplace but is perfectly fine when dealing one on one with people.
What I am getting at is for a developer to make something that XF would even remotely consider purchasing the sole rights to free and clear, it is going to have to be of a caliber that makes it impossible for it to be a $1500 or $2000 product. Think of XF, you don't own xf when you buy a license, you own just that...a license for a copy that you buy for $140 a unit.
I am talking about a professional developer is going to think of units sold and cost per unit and try to gauge the market they have that can use their product and figure out if the project is doable by them. Since a proper CMS is in it's own right a whole application = in the amount of work it does to a forum and since a proper cms built specifically for xf basically means building it on top of xf using it's permissions etc ...it would take much time to develop properly for what is a software specific application that requires an amount of work that is probably pretty close to what it took to develop xf in the first place who's only potential market is xenforo customers present and future.
The developer would have to feel fairly compensated for the work they did and be able to make a living doing it like any other job...if a professional php programmer works a 50 hour week doing nothing but coding a single thing they are going to get paid for once as an independent person...that at the minimum is 1500 dollars. I don't care who you are you are not coding a CMS that is worthy of becoming a core product in a week which is = to saying that I don't think any solid cms product is going to surface where the programer is happy with accepting 1500-2000 for a full on cms and this based on knowing what it would take to make one gauged against things I have done myself.
I hope you better understand my point now.