Really depends on a lot. Is it "stock" material for the inlay or does it need to be fabricated. Does the thickness match the field tile, etc.

Best to talk to your builder or tileperson. If it's pretty simple, I would say 2-300 additional. Pricing can also vary depending on your geographic location.

it's a mosaic that comes in pieces by sq foot. i'm attaching the picture here of the piece. we may have to forgo the inlay, we got an estimate from our builder that it is going to cost us 13K to install tiles for our 4 bathrooms?! We are going to bid the work out to another tile guy but it seems crazy to us that it would be that high! they are saying it usually costs 7 for 4 bathrooms but because we are using travertine in two and marble in the master, that it's 6K extra. we knew it would be some extra for natural materials but had no idea it would be 6 extra for a total of 13k.

That's a very pretty tile.

Just looking at that tile, you can see that even though it is mesh-mounted, there are slight variations in the gaps. If I was setting that tile, I'd be pulling any wonky pieces off the mesh and resetting them by hand. Even "perfect" sheets would have to be gone over after they are set in the thinset. While the thinset was still uncured, I'd take a putty knife and slide it through every gap, nudging everything into alignment. It really can be laborious.

But beautiful when completed.

Some installers might just slap it down, charge you, and call it a day. Others might be more meticulous. Labor prices alone could be $8-$30 a sqft for the installation.

I hope you get the installation you hoped for, it could be a stunning floor if done well.

Good luck!