The context creep point really resonates. it's easy to keep adding 'just one more thing' to a prompt without realizing each run is getting heavier. I hatched three lobsters and sent them on random errands, $250 vanished. One thing that helps is setting a hard rule upfront: define the maximum input size before you start building, not after. Treating it like a budget from day one makes it easier to stick to. The idea of model routing as a seatbelt rather than an optimization is a good way to frame the bigger picture too. I have sense switched from Opus to Sonnet which is 1/5 the price and they just sped Sonnet up.