A heuristic evaluation is not necessarily cheaper than a usability test. A heuristic evaluation requires 3-5 usability professionals because of the evaluator effect. Personally, I only have 2 usability experts at my company (including myself). Ideally, I would have 3-5 reviewers including at least one senior usability expert and one junior usability person. All would uncover different issues. I would also suggest including some subject matter experts (non-usability people).
“One of the biggest criticisms of HE is that it tends to uncover many low-severity problems or issues that aren't really problems (false positives). An additional practical problem is that multiple usability experts should be used. It can often be more expensive and difficult to find 3-5 usability professionals as it is to test 3-5 users.” - Jeff Sauro, 8/2/11
However, an expert review should be done before a usability test to make sure you will get good results and avoid trivial design choices. I would also suggest a pilot study (~2 users) before the usability test (~5 users per persona/profile).
My best advice is to use a variety of inspection methods (i.e. triangulation) to uncover most of the issues. Instead of just usability testing, consider expert reviews (or cognitive walkthroughs), heurisic evaluations and usability testing.