Eric Dane's GoFundMe Needed After Substantial Medical Bills

Eric Dane's GoFundMe is being questioned by some cynics ... but its purpose is more than needed, TMZ is told.

Here's the deal ... the beloved "Grey's Anatomy" star died last week at the age of 53 ... and shortly after, a GoFundMe began to benefit his two teenage daughters. But, as happened when James Van Der Beek passed -- some questioned why a Hollywood actor would need the cash.

A source close to the family tells TMZ … Eric faced substantial medical bills during his battle with ALS -- and the fund was started by friends to help his children … no one has to donate. So far, more than $355K has been raised.

Our source points out ... some donations have been $5 or $10, so people clearly understand the purpose -- and just want to help. Of course, there have also been substantial donations ... dropped by Hailey Bieber and "Euphoria" creator Sam Levinson -- who both separately gave at least $20K.

TMZ is also told ... Eric was single when he passed … and had been prior to the holidays. His only focus was on his daughters and one-time estranged wife, Rebecca Gayheart. His ex-girlfriend also posted a tribute mourning his death.