Looking at the wealthfront equity map, https://www.wealthfront.com/tools/startup-salary-equity-comp..., it seems like nobody in funded startups has more than about a percentage. Is that tool off, are expectations too low?
Ideas are very cheap - worthless actually, if you can't execute them into a product, let alone a product that users will actually pay for.
I don't know your current salary, but it should be a hell of a lot more than $100k in SF. So yes, 2% is low, especially given that it doesn't sound like there is an MVP or demo product existing - i.e. you would be building this as your role. Whether they like it or not, you're technically a cofounder, however as you're receiving some salary, you're not taking anywhere near as much risk and shouldn't receive as much equity as them - assuming they're not paying themselves.
I've had friends tried to recruit me in other parts of the country and gotten asked if I'm "king of my town" with what I'm making.
Agreed on the cofoundery-ness of it for the most part. They've been working on the idea and getting things fleshed out of the last 9 months and aren't taking a salary. I'd certainly like to make my way closer to the double digit mark, but honestly its tough to put forward much of an argument when the startup world is so capital centric.