Whenever I don't see a pricing page and need to get on a demo before I can find out costs I automatically assume its going to be expensive and move on.

Deciding which plan has the features I need.

Mailchimp, for example, lists A/B testing as a feature of their base paid plan, but if you want to test more than one thing at a time you have to upgrade to multivariate testing in their mid-tier plan. Similarly, if you want to send email in batches instead of all at once, you'll need the mid-tier plan, and would need to look through the fine print of each plan to figure that out. Customer.io's 2 plans and ConvertKit's single plan make it far easier to decide what to buy.

Each step of the process can be painful and is unique to the product/company

No pricing information is indeed the first indicator to move on. I like transparency on features and costs. Some products use "credits", if I cant figure out how that works I move on too.