The approval queue nobody budgets for.
The official Data API is free at low volume, and that number is the one every comparison quotes. The number none of them quote is how long it takes to be allowed to use it commercially. Commercial access runs through an application, a described use case, and a review that is measured in weeks rather than hours, and the outcome is a decision by a person rather than a provisioning step. That is entirely reasonable of Reddit. It is also a project dependency with no committed date on it.
The practical shape of the problem is that the approval sits at the front of the work rather than the end. You cannot build against production data while you wait, you cannot demo to a customer, and if the answer comes back asking for changes to how you plan to use the data, the design work you did in the meantime may not survive it. Teams routinely discover this in the second week of a sprint that assumed access on day one.
Worth saying plainly what this does and does not argue. It is not a claim that the official API is expensive or hard to use, because it is neither once you are through. It is a claim about WHEN you find out. A pay-per-call layer moves that uncertainty to the top of the funnel: you call it, it works, and you find out today whether the data supports the thing you want to build. If your timeline can absorb a multi-week wait, that flexibility is worth nothing to you and you should go direct.
One more thing the timeline hides: approval is not a single gate you pass once. Use cases change, and a use case that was described one way at application time can drift far enough that it needs re-describing, which means the dependency does not disappear after launch. It is worth deciding early whether your roadmap has one Reddit-shaped feature in it or several, because the answer changes which of these two options is actually cheaper over a year. A team shipping one integration and never touching it again is served well by going direct. A team that expects to keep adding surfaces is buying a standing relationship with a review process, and that cost is real even though no pricing page anywhere lists it.