Mughal-E-Azam would be for my grandparents era as even my parents were still kids. Comparisons should be made on a fair basis.
Bajirao Mastani is a dream project of SLB, true but is still based on an actual history. A dream project is worth spending that much. That's what Srk did with Asoka or Ra.One. It's exactly what Rakesh Roshan did for Krrish 3. And now Sooraj has done the same for PRDP. It's all about no compromises. And since you named Bahubali, it's SS Rajamouli's dream project & look how much he spent on that.
Bombay Velvet went down during the making itself. Neither the film nor it's songs excited anyone. Bajirao Mastani isn't going through that. It's clashing with Dilwale apart from that the makers haven't provided us with anything to doubt the film.