It's still a pretty profitable app for me and I actually enjoy the freedom of not having to have it go through review process.
For most mac apps people are googling rather than browsing the app store anyway.
I was also pricing it on my own website at $4.99 back then.
I realized that the value I was creating was more than $4.99 and I haven't seen a drop in revenue based on that.
So you have to find the sweet spot in order to afford keep developing it.
To me the icon indicating it's app store is this: https://developer.apple.com/app-store/marketing/guidelines/#...
But now you actually got me wondering if I should change it.
Edit: In fact, thinking about it some more, it's very clearly much closer to the App Store logo than anything else. It's literally the white silhouette design from the logo (as opposed to the colored non-sillhouete version from generic app icons), placed on a blue button that's similar to the app store logo's blue background.
The folder on my mac uses that icon for Applications.
Personally I thought that it would either open the app store, or that is was something related to Apple pay (although that one needs "[logo] Pay").
It felt a bit misleading.
I know they have improved a little but I frankly don't need them as the Mac appstore market is nothing like the iOS appstore market. There is no benefit really.