Does it make sense to pay Envato Elements a monthly fee instead of purchasing a WP theme outright? I am referring to building a single website and buying a single license, as opposed to a developer license for a theme.
There are certainly good reasons for both. There are currently more themes available on Market and you get access to basic support, but the Elements subscription model gives you access to many options for building your site all in one place including images, icons, fonts etc. So it will depend on you
If you need just one theme and then you plan to unsubscribe, then it doesn’t make sense. You won’t get theme updates nor support from Elements. WP theme without updates is IMHO worthless, because it is only matter of time till some WP version breaks some theme functionality and you will have to update to its latest version.
If you want to try different themes before deciding on one, then Elements make sense I guess.