"Technical skills make a technical success, but business skills make a business success" - business skills being about how to make your product "easy to buy". For example, a higher price can make it easier to buy, especially if it fits into a category of products that the organization is used to buying - and in the way they are used to buying them. It's part of "positioning" it in the customer's mind. This is all simply seeing it from the customer's point of view. These things don't directly improve your product, but they do help to communicate it to other people, which is also intrinsically worthwhile.
The economy is bad and perhaps also comp sci is finally ending its multi-decade growth phase. There's always a place for anyone who creates value, but perhaps the days of "it's raining soup grab yourself a bucket" are over, and a different strategy is needed (Disclaimer: this is a guess. I'm not yet sufficiently deluded to think I can predict the future).
More generally, I think I have had exactly your dilemma (and still do). I don't have a solution, but perhaps some camaraderie. It's the philosophy of doing whatever does the most good. It feels good (and I think it is good). I believe that if you create value, someone will work out how to pay you. It's a wonderfully inspiring and freeing philosophy - and it makes me feel happier and feel like a pure, innocent person. Also, people want to help you. And for me, it was also inspired by Bucky (his epiphany by the lake - which some spoilsport pedant has apparently debunked as the exact place for it, claiming it's more like a constructed founder's story. Anyway).
The disillusionment for me was in open source: for a developer tool I wrote, people took the help I provided, but didn't give anything back [1] . I did have sales [2], but because there was no pressure to pay, huge organizations would take 3 months to pay [3]. I really hated waiting for the other shoe to drop [4].
Today, I believe that if I create value, it is OK for me keep some of that value. This seems to be right and true... but it doesn't make me happy, and it isn't inspiring or freeing.
I'm currently working on a patentable enterprise developer tool, that I plan to initially sell at a high price to large organizations. As the tool becomes more general, I will lower the price, until eventually it is cheap enough for anyone to afford. I think this is good, and sensible... but it also makes me feel a little sick at heart. So I don't know the answer, but hopefully I've offered some camaraderie. Do let me know if you work out an answer! :-)
[1] which is part of the open source deal - I just didn't like it
[2] dual licensing, like Ghostscript
[3] to be fair: everyone who said they'd buy it, did eventually buy it
[4] I'd much prefer they didn't tell me they were going to buy it,
so I didn't have to worry for 3 months.I'm not asking anyone else to fix this for me. It's my responsibility to find my place in this new market in a way that let's me contribute and benefit. I'm glad to know my observations aren't just loony (or at least that I have company).
Alternatively, though it is also distasteful from a "give away and trust" perspective, you could overfill the talk with teasers and upsells -- that is, to speak to a larger audience uncompensated, it will necessarily be more a sales pitch than open conversation. ("I can answer that question on a 2-day consulting contract." "I cover that in my low-priced video series.")
Or, the condition for them videotaping could be you get a copy, they can't offer it on the open net, and you have the right to use/sell the video elsewhere. (This might get gummed up in their legal process and thus be a de facto 'no deal', but it's another way to propose splitting up the gains from your talk.)
So while there's always a point you may have to withhold your full output, there could also be other zones of agreement. While a Bigco can be obliviously greedy in some dimensions, in other dimensions they don't mind throwing off value others capture.