The entire point of taking a VC check is to run your business at a loss while you grow. The idea is to jump quickly from $0 to millions in revenue instead of having that journey take years. So you hire good people, pay them well, spend on marketing (in some businesses) and take on customers at terms that are break even just to have customers at all.
You learn if you have product market fit but you may not learn if your prices actually sustain your business. And then you can either raise prices (hard) or fire people (hard) to get to profitability . Or just raise more VC money and “make it up on volume”