My total database is maybe 400 gigs. Most of the writes overwrite existing data, so storage cost isn't a concern. With the cost of an upfront RI for the year on RDS (with basically as many iops as I can use), your solution gives me ~100 million reads. That's...like a month of usage at best.
At least I'm my case, the fundamental problem you're facing is that reads are just too expensive. Writes and reads tend to grow at the same pace in many products: there's a ratio that tends to stay the same as you scale. $20/million reads is just a _lot_. The ratio of writes to reads for your pricing needs to be 100:1 or more for it to make sense for me, but I'm more like 10-20:1.
> I guess I’m hesitant to put time into documentation and similar, if I can’t somehow find a steady stream of sales prospects.
This is part of why a database company is hard to build. You will simply not find anyone willing to give you money, because the alternative is going to be a solution your customers already know and understand and which is likely extremely mature. You're competing with Postgres and Mongo. You can't ship a database product that doesn't work: you're asking people to build on you for their storage primitive. If you fuck up, that's a business-ending event for your customer. You've either got to come to the table with an extremely compelling product ("I couldn't build my business without this") or you've got to show why someone should trust you over an established but somewhat more expensive alternative.