More expensive = better?

I believe that audio gear is much like wine.

A 2018 Pomerol or Saint Emilion Grand Cru is fabulous, but is it twice as good as a bottle that is half the price?

No. It is almost always a case of diminishing returns. 

No it won't. Not jaw dropping. Why should it?

In fact it might not even sound better than a $100 one.

It's far more important to match the amplifier to your speakers in terms of power and drive.

A second opinion, preferably a non audiophile one, might also prove invaluable when auditioning.

Bear in mind also, that certain features can prove useful, eg a mono button or a balance switch etc.

"My speakers are under $1k, staright up, midrange surpasses Wilson's biggest guns, Dali, Sonus Faber, Rockport, none beats my midrange. Under one K bucks"

Hyperbole aside, what about the low end and the high end?

Sound is only as good as its weakest frequency range.

You are the music while the music lasts.

TS Eliot

A good $8,000 amp will sound much better than a good $800 amp, that’s for sure. Jaw dropping? Only if you were clever/lucky enough to choose an amp that perfectly fits your setup.

Also bear in mind that for your jaw to drop you need 1/ To be sophisticated enough to appreciate a high quality sound reproduction. 2/ To be able to build a coherent setup/room system to give a hi-end amp a chance to show you its’ class.

Otherwise you can buy a $30,000 amp, plonk it on your hi-fi rack, and it will perform to 30% of its capability. Just like a $3,000 amp. So many people have done exactly that and claimed that there’s no difference.