Turnover per hour is the most practical difference for a budget. At roughly four seconds per ordinary spin, an hour of play at one unit costs around 900 units of wagering, most of which returns to the balance along the way. Comparing bonus buy vs regular spins at the same stake, an hour of purchases could easily push wagering past 3,000 units if a 100x feature is bought every two minutes. The house edge applies to that larger figure, so the expected hourly loss scales up accordingly.