Depends on the type of floor, some just click into place, some need to be glued. Also depends on the room lay out, big rectangular rooms should be less than irregular shaped small rooms.
However for fit only that seems expensive to me. I previously paid €10 per sq metre, for admittedly a basic job.
All depends on the type of flooring and the quality of detailing around the sides, doorways, etc.. Are skirting boards being removed/refitted or trimmed? Architraves trimmed? Or just the nasty trim laid all round. Some examples here of the variation for different flooring types. No idea what they're like though, I've done all my own.
Herringbone is tricky to get right (having done my own 20 years ago!). The blocks I had were 200mm * 60mm and had to be stuck to concrete. It then needs sanding with a rotary sander and sealed twice with the best polyurethane varnish you can buy. Done well it looks the business so whoever is charging that amount for it needs to be good so verify their work before agreeing to their price.
My living room is 30M2 overall. If it is block as I described, then you may want to consider a double bead straight run around the skirting boards and fireplace to give added effect to the herringbone pattern contained within.