There are only two priorities for a start-up: Winning the market and not running out of cash. Running lean is not an end. For that matter, neither is running fat. Both are tactics that you use to win the market and not run out of cash before you do so. By making “running lean” an end, you may lose your opportunity to win the market, either because you fail to fund the R&D necessary to find product/market fit or you let a competitor out-execute you in taking the market. Sometimes running fat is the right thing to do.