Using Deepseek v4.1 Flash on something like GreenGPT is probably about a euro a day if you use it all day. Hard to see how that is 5x more expensive.
For my usage almost all of those tokens are cached input, which is why the cost is so low.
Your token usage absolutely scales with parallel agents. So.
Anthropic doesn't really publish their limits so it's hard to do a direct comparison when these things come up. I just have doubts that DS 4.1 Flash is remotely close to 5x as expensive. Also, I've seen a lot of people claim that switching to it cuts their costs by a huge amount, which based on API per token costs of Claude seems to be far more likely.