That sounds about on par for the level of appreciation you get for doing good things and giving the results away for free online. I know from hard experience of my own. And just yesterday there was a thread on the Reaper forums by the guy who did the Sonatina orchestral sample library, he’s tentatively working on a new version, and when someone made a suggestion for how the new version should be done, he went off on a rant about how few donations and how little feedback he got for the original Sonatina project.
He says he, optimistically, has made around $100 in donations since releasing the original Sonatina circa 2009. And the Sonatina orchestra is Internet-famous among people who work with samples and samplers, everyone has heard of it and very, very many people have used it. I’ve used it a lot, even made Renoise instruments out of most of it, and never donated or even sent a “thanks” to the guy either (until I saw that thread yesterday, that is), so I’m no better. In my own defense, and this probably applies to others, having visited the Sonatina homepage, it felt like an abandoned project, as though the guy finished it, dropped it online, and forgot about it. There was no visible evidence that the producer was still behind the scenes actively looking for donations and thanks, so there’s that.
So, it’s a sad comment on people’s internet etiquette, but even a project as relatively high-profile as Sonatina gets almost no constructive feedback and virtually no donations despite the fact that probably tens of thousands of people have actively used it and it took a lot of work to make.
If you’re going to release anything for free online, you have to do it with the expectation that you’ll get nothing out of it other than perhaps the mostly silent appreciation of the end-users (which is nice but won’t buy you a coffee). One approach that seems to (sort of) work is to do blog format, like the bedroomproducersblog guy, and constantly release and link to freebies every day to keep people coming back to your site looking for them (thereby also seeing ads you sell space for). I’d love to know just how much revenue the bedroomproducer guy makes from his site. At any rate it’s a good idea to give him a heads-up when you release something free, he’ll sometimes do a feature article on it and then it gets a lot of attention (for a day or so, anyway).
Edit: BTW, OP, there’s a guy out there who’s had some success selling VST interfaces for several synths, you might want to check out his business model if you intend to start charging for what you’ve made, his page is: http://www.vst-control.de/