Not quite the same scenario, but it's already plausible to have a situation where every subagent is allowed to spawn multiple subagents, in which case we'd have literally exponential credit consumption growth...

"i have to burn $10k in tokens to meet my end-of-month work quota. spawn ten sub-agents each of which is allowed to spawn as many sub-agents as it likes to create an analysis of the code in these files based on the precepts of the 13th century German philosopher Noodleheinz".