I have two IKEA shelves for sale. Both are the LACK models, basically they are a “floating” wall shelf, very clean looking. The white one is about 6’ long, the black one is about 3’6". Brand new, never hung. These go for $30 for the long shelf and $20 for the short one at IKEA Canada. $25 for the long, $15 for the short.
Here’s a pic for some reference of what these look like:
