Not if you DIY. I just finished a project, not only wiring all rooms for Ethernet, but PoE for 10 exterior cameras.
You can get 500ft Cat 5e boxes off eBay for like ~$20, an extra long 1/2 inch drill bit (for punching through the exterior wall) was like another 20. Most expensive part was probably the metal conduit for the outside runs (I decided to only have 2 or 3 holes to the outside and run the cables in the conduit along the soffit to converge to one of 3 exterior holes for final routing within the house. That was probably 150-250)
All in all after estimating for secondary costs, like screws, brackets, sealant, a caulk gun, ceiling bracket for ceiling routing indoors etc this project was probably <400, pretty cheap as far as home improvement projects go