You might not be able to "just buy 3 more boxes" as the dye lots will probably not match exactly. Not a problem if you don't mid mixing the tiles up before install and having some variation once finished.

I always fall in love with expensive tile, so the price looks low to me!

Emser makes a decent tile. If you want cheap(er) tile look at Floor & Decor, but everything has gotten more expensive these days.

Thanks Chispa! I am going to look at a local tile store to compare prices for plain white subway tile.

It isn't a ”subway” tile. It is technically a mosaic, on mesh. Mosaics are always more expensive than field tile. Subway is 3x6, and is set individually, not in sheets.

Thanks for the info. I really don't know anything about tile. It seems like it would be easier to install a mosaic rather than individual tiles - is this correct?

Not necessarily, some mosaics are a PITA to install and hard to do properly, like penny tile mosaic sheets.