What it costs comes down to scope. A single workflow, like automatically tracking pump-out due dates and sending reminders before a tank backs up, is a narrower build than a system that also handles route scheduling, inspection reports, and permit paperwork. The more parts of the operation it needs to touch, and the more it needs to connect to tools you already run (your CRM, your scheduling software), the more there is to build and test.
The other big factor is whether you want it built and handed off, or built and operated. A build-only engagement ends once the system works and it's yours to run. Build-and-operate means we keep it running: watching for failures and retrying what didn't go through, then flagging the cases that genuinely need a person, like a customer disputing a bill or a permit office asking something nobody has answered before. Operating something long-term costs more than building it once, because someone has to keep paying attention to it.
There's no price list because the value differs too much from one company to the next. A pump-out reminder system that recovers revenue you're currently not collecting is worth something different to a small operation than to a large one. We quote each engagement on what the system is actually worth to the business running it, not on hours worked. The honest way to find out what it would cost you is a short conversation about what's repetitive and eating your time, and what a system can safely be trusted to decide on its own versus what still needs a person.