I wouldn't comment on the quality (or lack thereof) of open source software compared to their main commercial competitors, since I haven't enough experience of the former to make a proper judgement.
What I would say though is that just because the software is FOSS, that doesn't mean zero cost.
Sure, you don't have to buy licenses, but you still need all the infrastructure to deploy it, and especially to support it. If your users have more difficulty using the open source alternatives for whatever reason, you will spend more money on staff to provide sufficient support. If your support staff aren't good with it either, you might need to invest in training courses and/or more qualified staff. Heck, you might even need an expensive support contract with another company to provide 3rd line support.