The fact that 25% of the web is powered by it doesn't mean 25% of the web will actually pay for your solution - they might pay for a third-world competitor's one that's 10x cheaper, or they may not pay for anything at all.
I would also be skeptical about the amount of money you could make on WP vs Laravel or a similar framework. A WP plugin is relatively hard to sell at a good price (let's be honest, with a 100$ price which is pretty steep you're only recouping a little bit of the time spent developing the plugin, and I'm not even talking about mandatory tech support you'll have to provide). Excluding a few outlier plugins that have exploded in popularity, a PHP developer's job at a company or as a freelancer building quality products will earn you way more cash.
Of course this assumes you want to do legitimate business - if we go down the scammy route you could pretty much sell anything - even an empty PHP file - there are a lot of idiots out there who'll happily buy your "magic" plugin based only on your (fake) sales pitch.