When it comes to buying products and services, at a personal level, most people I know who've checked the work of people they've hired for things like home renovation or accounting have found grievous errors in the work. Although it's possible to find people who don't do shoddy work, it's generally difficult for someone who isn't an expert in the field to determine if someone is going to do shoddy work in the field. You can try to get better quality by paying more, but once you get out of the very bottom end of the market, it's frequently unclear how to trade money for quality, e.g., my friends and colleagues who've gone with large, brand name, accounting firms have paid much more than people who go with small, local, accountants and gotten a higher error rate; as a strategy, trying expensive local accountants hasn't really fared much better. The good accountants are typically somewhat expensive, but they're generally not charging the highest rates and only a small percentage of somewhat expensive accountants are good.