You could say I happily paid for an experience.
can we ask what these suggested changes acted upon were?
I have maybe about the same number of active bikes as you - more if you count others.
I know sod all about the "science" of bike fitting and everything I read about it brought back fevered memories of O level maths and physics.
Gradually I found that all my bikes, of various frame sizes and geometries, had gravitated towards the same key measurements.
Essentially by listening to my body - well that and two catholic priests I fell in with one moonlit dunwich dynamo many years ago - they told me my saddle was too low.
I did more recently have a bike fitting on a jig refundable as part of a bike purchase - I bought the bike.
Nice as the guy was - and careful and methodical, and sincere, with no bullshit, his guidance didn't feel quite right. I went with it. Rode the bike for a bit - feared I'd made an expensive mistake - went back and gave him my practically arrived at measurements - he flipped a stem and pretty much conformed the new bike to them. And since all has been well.
In tune with my body.
So I'd need some convincing that a bike fitting is needed for anyone who has a small number of bikes to tinker with.
Some folks of course search for supposedly optimum power output or whatever but that isn't my world, and nor is it yours as you say. Those folks it seems to me are prepared to put up with all sorts of contortions in search of their goal - and emulating their drug-fuelled champions.