I'm not a "real expert."
The concept behind higher-grade instruments is that a player spends an incredible amount of time with it, constantly training precise muscle movements. This can make what seem to be relatively tiny differences feel huge. If you practiced on a M3 for the last 10 years, it is not surprising that your vibrato would feel/sound different on a Les Paul Studio.
I would caution that almost anything that makes you sound different, you may falsely perceive as sounding better. Think of the people who go overboard on wah, fuzz, delay, reverb, etc, when your ears are just begging for the clean channel.
As for the worth of expensive guitars, my personal and rather cynical feelings are:
If you can afford it, you probably can't play it.
If you can play it, you probably can't afford it.
If you can play it and afford it, well-done sir.
If you can't play it and can't afford it, nice to meet you and I hope we find ourselves in a different category in the future.