Is it realistic to suggest that users == money in this space?
In my opinion, no. Users represent potential, but not money. The term "users" is highly generic. Are the users casual or vested? Open source draws a high number of casual interest, especially early in the life cycle.
Where does the true value transaction take place?
For users, the true value transaction is the utility derived from the product and the speed at which they can use it. They aren't just free financially... they free up time and overhead. It's the perfect way to perform a more in-depth trial and see if it solves problems in your unique circumstance. I'd sum it up as "flexibility".
The business value is built over time. Most open source revenue is generated in services (add-on, consulting, etc) or using a commercial open source approach. It's all about reaching new customers or increasing the value of existing customers. When people invest time to use open source, they're investing in the project leadership. In some sense, it's similar in some regards to creating vendor lock in (like SugarCRM).
Is this a space where the big players are willing to pay large sums of money to fight for traffic and control of the development culture?
Nobody other than the big players can provide a definitive answer, but my personal "nutshell" answer is"sometimes". However; I believe it's less likely to see investments in outside companies.
For example, Google, FB, Microsoft, Amazon, etc all hire developers specifically to work on open source projects. Sometimes these projects spin off, but it's an organic process (not like fundraising). Look at Bootstrap, or the newly formed npm, Inc for examples.
In my opinion, things like Meteor.js are NOT the norm, and you'll notice their lead investment came from a VC, not a major tech player.
As for gaining users and contributors...
I have several friends who have built successful and well known open source companies from scratch, but none have been sold. They were all bootstrapped to profitability, and each of them found their own market. Users became contributors. Contributors became employees. Personally, I launched an open source visual desktop web server this summer. It offered significant value in convenience via simplicity, and this resonated with developers. I've had 12K downloads in that time, so it's not a huge market, but it's also not "just another" Github repository. I created a more professional website than the average open source project, and I blogged about the use cases. I made YouTube videos and setup a mailing list. I found my audience by looking up readership numbers and targeting syndicate blogs... then I contacted those publishers and pointed them to the website. I put a lot of leg work into it, and I made it work without a monetization path. My software is incredibly simple (the main draw), and there have been a ton of enhancement requests. These requests have started turning into private messages like "I'd pay for _____ feature".
The bottom line is, in my humble opinion, there is no quick way to launch an open source business. Those that have are the outliers, not the norm. These things have to grow organically. If you can't recruit a partner in the beginning, then you have to build the software yourself. You have to prove momentum... and that means investing time and/or money.