What is with you people?
Plugin developers working as much as you do and maybe more. And it is as simple as that; developers need to make a living as well.
An average price of the add-ons is $30 per year when the average hourly rate of a developer is $50 ( or more ). So how can that be expensive, seriously !?!?
By constantly updating the core plugin and the add-ons developers make sure that you up to date with your site. If it is security, bug fixes and new features. And so, if the developer is constantly working on the plugin and you keep receiving updates it makes sense that the developer will keep getting paid for his time. It can be weekly, monthly, yearly and so on.
You can choose to either by an add-on or not ( if you think the price or terms are unfair ) but regardless the choice you make you still need to respect the developer choice of price and terms. And you have the right of course to give your opinion about the price of the add-ons but giving a 1 star review because in your opinion the add-ons are expensive or because you think that everything should be free is unfair and insulting.
A review should be about the functionality of a plugin. about how well its features work, about performance, errors, bugs, warning, code quality and so on.
From my experience, if you are trying to build your business only by using free plugins and themes or if your business does not produce enough to cover the expense of few add-ons a year then you are in the wrong business.