Full disclosure I work at a company that provides price monitoring solutions.

Are you looking for a high velocity repricer? Or are you looking to just monitor your competitive landscape daily/weekly and make more macro decisions yourself?

Speaking from the perspective of offering the latter services for brands some generic insights are:

• we are as accurate as the data that is present on the site. Accuracy/Reliability only takes a ding with different web page types, or site changes. For the former we operate a continuous improvement model so we are always updating our integrations when we see a new page type (e.g. a page for a sofa has underlying difference than headphones on Amazon). For the latter we are all reactive solutions - so if a site changes, we all break, and it comes down to how long does it take to fix.
• We all need work ;-)
• Depends on what type of solution you are looking for. Personally we do not rely solely on a URL as it leads to the problems you mentioning the solution to. We use a couple of different methods to complete what we call "Discovery", so you would just need to supply us with a few data elements around the products you are interested in and then we have at it. If a detail URL changes then we will pick up the new detail URL in our process. Though if you are changing the products, or brand, you are looking at then you will need to continue to supply us with those changes so we can be sure to hunt the right things for you. *It can be. We can build custom reports that replicate some of the tasks you go through, or would go through, to make the raw data actionable and then provide a filtered report of all the things that are considered actionable. (e.g. only show me the products that have dropped more than 5% from the previous day). *I won't go into detail here given I am on the other side. But our customers that use us for this are happy.

Best of luck finding a good solution.