What 500 is offering is very fair for very early stage startups. Dave and his team run an awesome program. The top accelerators these days are pretty close to these $ and equity %'s and the top accelerators offer tremendous value for companies lucky enough to get in. Just stick with a top 10 accelerator. There are thousands of accelerators around the world these days and I find that most add little material value.
The market is also starting to see venture accelerators experimenting with new models. In 2015 Dreamit experimented with a new "zero/zero" program where we invest $0, take 0% equity, and ask for a discounted investment right in the company's next qualified financing round. It's great for later stage startups that are post seed / pre series A where they don't need the "stipend" cash but instead need the network, customer connections, partners, mentoring, acceleration, etc. Dreamit will continue with both stipend-based and this new zero/zero funding model in 2016 with special vertical focuses in digital health and ed tech.