This entire argument rests upon the fact that Gemini Flash ain't cheap.
Try plan with opus 4.8 and then implement with Deepseek v4 flash - its 35x cheaper for reads, 90x cheaper writes, and 18x cheaper cache reads.
Or plan with Deepseek Pro, or even Flash itself. I've been impressed with both.
+1. i have similar workflow and i use local models on igpu so token cost is free and electricity cost is in cents.