Right now - there's some heavily subsidized subscriptions that are more or less cheating. For instance, Github CoPilot at $39/month gives you claude opus 4.6. They're going to close that off, but right now it's like a freebie for those doing API agentic harnesses.
That said, if you are doing always on agents and you spend $3k-$4k on a GB10 or, $5+ k on Apple Silicon as your sunk cost, you will probably come out ahead.
I've got 5 agents running a purely experimental social experiment. AThey operate in an evennia mud (a familiar sounding city called "gothmud). I've built a channel, idle prompts, sleep schedule. I feed in real world news, weather. There's a character up in a clock tower that reads evennia's audit logs every 20 minutes to surveil the city, and a cast of people wandering around, investigating things, having coffee, repairing robots. This is all hitting qwen3.6-35-A3B on the Asus GB10, which cost me $3k.
Over the last 30 days, I've hit 394M input tokens, 1.6B output tokens. I would have spent between $1600 to $1700 if I was using openrouter. Not calculated - I also have comfyui running in the spare space, and the agents "take photos" of the rooms they're in, selfies, workshop photos, etc.
How much did I spend on electricity? I don't have a meter on my box. My total electric bill for the last 30 days was $220, so I know it's less than that. My rate to compare is 11.7/kwh, but it's closer to 15c/Kwh total. The Asus GX10 has a 240W power supply, and it's probably only pulling 180. I estimate $15-$20/month. But worst case red-lining. 240 Watts, 720 hours = 172KWH , and at $0.20, I come to $35
Here's the kicker thought - that github copilot subscription I mentioned? I have another agent running on that, reading all my other agent logs, managing my obsidian notes, doing research, sending briefings. And all by itself, it used almost the same amount of claude-opus tokens for that $39/month subscription. I was actually a bit shocked when I pulled a recent report and saw that. I'm working to migrate functionality away from copilot subscription to the local model. A lot of the initial setup might have needed it, but not the ongoing review style work it does.