Different bookmakers price the same market differently, routinely by 5–10%. Taking 2.20 instead of 2.05 on the same outcome is a 7% improvement in return for zero additional risk — compounded across every bet, price shopping alone often separates a losing record from a break-even one, and a break-even one from profit.
This is the easiest professional habit to copy: hold accounts at several bookmakers and always take the best available price. It is also the backbone of value detection — our model compares each book's price against the margin-free consensus, and each match page lists the best available odds per outcome so the comparison is already done.
Your average bet is at odds ~2.00 and you stake 100 × £10 a month. Systematically taking prices 4% better is worth about £40 a month — the entire margin handed back, before any predictive skill.