Firms you'll see elsewhere, and why they're not here
Metalab is the obvious absence. The studio designed Slack's original interface, twenty-four of its clients have reached unicorn valuations, and it runs a venture fund investing at pre-seed. It is also reported to start small projects around $100,000, which puts it outside this page. Worth knowing about for later, and worth approaching once you have raised a Series A.
Netguru carries a documented minimum near $50,000, and Focus Lab starts at $25,000 with a strategy-first process aimed at growth-stage rebrands rather than first products. Both are strong and both are premature for most startups.
Superside is a subscription for marketing creative volume across many channels. Useful once you are running paid campaigns and launches simultaneously, wrong when the problem is inside the product.