Charge more than 3k if the outcome will be so high for them, explaining this to the company. Its an investment on their behalf. They don’t believe in the product at all if they’re not willing to pony up some payment. Sure, they hope it will work so they “make millions”, but they still have jobs if it doesn’t, no big deal, next project, find another Industrial Designer who takes the royalties agreement bit.
I have no firm statistic to say it doesn’t work X amount of time. But you can be sure the odds are against you. I’ve been offered equity and/or royalties many times, and have taken the offer many times. I haven’t ever received a royalties check yet during my career. Trust me, I’m a risk taker, probably more so than most on this board. I don’t have a house payment or a wife or children, so I can afford to make risks, and yet, I still haven’t received a royalties check. I’d say the odds are that a royalties offer you get will fall through, for a number of reasons, and reasons that aren’t even intentional.
Guaranteed payment versus “you might get paid if we don’t screw this up once its out of your hands”.
Sure, risk vs reward. But for me, I really like to be able to make my insurance payments and pay for groceries, rather than hopefully be able to buy them later down the road.