There's no way I could put a price on all of it, wouldn't know where to start. For a box of say 10 men, you're looking at £15-25 depending on army.

Basically what you've got is a lot of Space Marines, but then they're split into different 'factions' such as Imperial Fists, Space Wolves etc, but they're the same at the end of the day just painted differently so just advertise them as Space Marines, much easier lol.
The Hammerhead is from Tau I think, another army, doesn't look like any other stuff from them though.

I don't recognise the invidiual Epic stuff, if they're metal then they're not cheap new.

You need a snotty little nerd to identify everything really

Generally everything you need to know is on the boxes, although some of it doesn't look 40k to me, looks more like early Warhammer.

Sorry I can't be of more assistance.