for minor acts this might for sure be true. but it also depends on the kind of music you make and how popular it is. commercial bands playing radio-tunes or dance music are generally booked very often and i have seen some of them taking 8.000 Euro and more per gig, giggin 60-120 times a year. thats quite a bunch of money even if half of it goes to the tax. and i also have seen this amount of money beeing payed for some metalbands in germany - even some realtively unknown to the "outher world" ones.
There is definitely some money out there for musicians in most genres. it just depends on what sacrifices you are willing to take and how much work you want to invest. but to get to a point where you can get 3000+ bucks for a gig definitely takes a LOOOOONG time and much effort.