From my experience, the cost of WMS software usually comes down to customization. In manufacturing, no two workflows are exactly the same, and the more adjustments a system needs to fit your processes, the more expensive it gets. Choosing a solution that fits most of your needs out of the box can save a lot in the long run.
I once worked with a retailer in the process of selecting a warehouse system and, once again, the hidden cost came simply from customization. While the starting license seemed affordable, it was only after they added multi-supplier workflows and Shopify integration that total costs skyrocketed by 40%. Reminded me of MOQs when you are considering factories located in Shenzhen. You think you are saving a buck, until you realize you are paying transactional fees to set the single MOQ up. As obvious best practice, we always encourage clients to map out processes (use a spreadsheet) before signing a contract so that they understand what custom modules are going to cost before they commit to tens of thousands of dollars. At SourcingXpro, we always suggest to our clients that they first test a $1,000 MOQ and once they are confident and their testing is justified, then they will expand an additional arrangements. That first step is all we mean by small scale first, then scale once the math is easy to verify.