One key of platform business models is to solve the chicken-egg problem, mean to achieve the critical path especially for start ups. If in the first stage of your platform project you focus to much on profitability, you will probably not be able to achieve the critical mass. Focus should be raise of interactions between platform participants and getting a relevant number of active users. In the further step you can focus on profitability via transaction monetarization

Second that, depending on the maturity of your platform and the type of value created, the focus should be on growth instead of profitability. However, there are also platforms for which you should prove early on that a transaction holds value that you can monetize. So, without more context this is difficult to answer.

I 3rd that. Network scaling, interactions, interactions 1st! Figuring out how to make that metric work in the platform business model is probably the toughest Everything else will fall into place after getting that metric right