i think formal lessons instructors are rip-off artists just because of the fact that in my experience, all of them charge BY THE HOUR...
i am not saying they are cheating on you or anything, but IMO, drumming is A LOT about muscle memory. say that beat in Rosanna, while your brain may get that concept of triplet shuffle, your muscle memory doesn't. so what you do is pressure your self to learn the songs at the normal tempo (which of course is fast for your virgin drum muscles), and you end up being a sloppy drummer.
same thing with double pedals... you know the bass drum goes dit-dah-dit-dah sixteen beat while you hit the snare on the 2 and 4 ... your brain knows that but your muscle memory would take weeks to adjust to that, and by that time, your instructor had robbed thousands of pesos off you from one BASIC concept that even your kapitbahay drummer knows about.
i am just so happy that nowadays there are drum forums and youtubes, and all of these "beginner" instructors arent ripping-off kids as much.
right now, im learning drums and loading muscle memory patterns in me. i watch a lot of youtube and pick up lots of gear advice from here (techniques are better seen than read)... and im not being ripped off.
ive been to different instructors both with bass and guitar, and i realized none of what they taught stuck.
after paying 3,000 pesos worth of bass lessons, i know how to do some parts of rio funk and slap a pattern in G. for 3,000 pesos, i can pay someone to record 5 slap patterns or well, id just buy two DVDs and just be sure i have a player that can slow mo it.
IMO, you should get instructors when your muscle memory is more than adequate to handle patterns at a snap. that is so you will be learning concepts, theories and opinions. if that instructor is good, he will transform the way you approach the instrument... if he is like one of those talented instructors who capitalize on their skill, you'd end up not learning anything and be left wondering "how did he do that?"
and id also appreciate it that an instructor knows [gooey brown stuff] about gear. with my bass experience, my instructor doesnt even know the pedals in my board, and couldnt even have basic conversation with me.