Are cheap levels actually accurate?

It depends. Specialist-community threads (including r/harborfreight) note that even inexpensive box-frame levels can read as accurately as a laser for general work, and budget torpedoes like the Firecore draw thousands of positive verified-purchase reviews. That said, at least one retailer reviewer flagged a budget torpedo as 'not accurate,' and reviewers consistently recommend checking any new level against a known-flat reference in the store before trusting it.