It can be because there is no cap I make however much I can convince someone to pay me for. Working in TV/Film is not even close to the awesome adventure people think it is. Its all types of fun but there is a lot of bullshit you have to deal with the phrase starving artist applies heavily here....and people try to take advantage of you like crazy. You will be pretty much a bum for at least 5 years before you get your name out there enough to make money.
Being a freelance you have to look at it on a case by case situation. The day rate changes from state to state (A Michigan Camera op should make 200 bucks a day w/o is own gear and 350 with) an ENG audio guy should float around 150 to 200 bucks a day or 35 an hour. A day is 12 hours. Those rates go up depending on your skill level and how popular the "thing" that you are doing is. A camera op on Lost will make a shit ton more than one on Random cooking show. I am a Camera Op, ENG Sound Op,Boom Op and Stagehand those skills will allow you to demand more money than lets say a set PA.
I am kinda confused by what you mean as grunt work...
But each company has a different rate depending on what they are doing the skill set required to preform it and how long you are going to be doing it for within the budget of the project. It also depends on whether you are in a union or not (I am not) or whether you are staff or not. I am a freelance but many people work on the same show for years and that is set up kinda like a regular job with rises and such.
When I worked for MTV's Made I made 35 an hour, when I preformed the same job for TruTV I made 150 a day. The next week I made 10 bucks an hour cutting some of the worst concert footage together I have ever seen. Then made 75 bucks a day pulling cable for ESPN. Hell when I first started I got paid in Pizza coupons so I could actually eat. It also takes a endless amount of networking skills to get your name out there.
To Long Didnt Read version.
Yes it is very lucrative but it takes a really long time to get to that level unless you catch some breaks along the way. I didnt make shit (and I mean I literally posted a negative amount) the first 3 years of my career but now I am at the point where I am making a decent amount and hopefully in a few years I can command mid range money and then after that I can command top dollar.
I hope that answer your question....working in media is a cluster
because there is no one way to do anything. Also it is very common to take less money to do something cool. I often will lower my rate to work for MTV because it looks great on a resume, same with movies. To have my named linked to a well known movie is worth taking less or no money.