Another dark pattern is the use of credits. You subscribe for $X/month. That buys you Y credits, which you then spend at different rates depending on your usag

Another dark pattern is the use of credits. You subscribe for $X/month. That buys you Y credits, which you then spend at different rates depending on your usage. Some services are credits per minute, some are fixed credit amounts. Not only do you have to guess your capacity requirements, you also then have to translate that into a series of tiered variable costs and fixed costs, and translate from credits to currency (often working through bulk purchasing rates) to figure out how much you'll be billed. I manage a SaaS contract that bills like this and I'm not sure I've ever accurately predicted our bill. Also one of their fixed credit cost items is clearly 10x more expensive than it should be when you actually work through the numbers to see how much it costs.