A few of the additions beside allowing to reply reviews are:
Filter / sorting
and may more.
I know this is cheaper, but for the price it doesn’t really have comparison (it’s just the double of the price but it’s fully featured compared with yours offering only 1 functionality). And that’s only one, there are a lot of plugins out there. Hard to compete with them.
Would it be crazy that you improve the plugin even if it is as a cost increase?