If you worry about sending your data off for inference, Fireworks is one of the companies serving open models with solid performance and compliance/zero data retention sorted out. OpenCode supports them and many others. Cursor uses them. They don't have the super-cheap cache reads deal that DeepSeek's own endpoint does, but are still well below Anthropic API rates. (Though crucially you're not paying API rates now!)

DeepSeek and Xiaomi's deals on cache reads go with their models' latest gens making caching cheaper (using less space for KVs). No open-model inference provider has decided to match the pricing. I'm sure that says something about how inference pricing works, but not completely sure what.

Agree with others that top open models aren't on the frontier, and I would expect differences doing big-picture planning or anywhere you're only giving broad brushstrokes and looking for a lot to be guessed. But they do seem fine at coding from a a concrete plan! No experience in huge codebases because I only use them outside work, but they seem good enough about gathering info before they dive in that I'd expect them to grep around as they need.

An annoying caveat: individual subscription plans, used heavily, are much cheaper than the API -- see https://she-llac.com/claude-limits -- which complicates any argument about cost. I still think open models are worth playing with. They're one of the things that let us treat this as a technology rather than just as the product offerings of one of a few companies.