Using exclusions or quotes around keywords disables many of the "smart search" features, such as keyword substitution and automatic category navigation.
A search for $2 bill or 2 dollar bill will be automatically steered into the following category:
Coins & Paper Money > Paper Money: US > Small Size Notes > Federal Reserve Notes
If you try the same search but use an exclusion term, the exclusion prevents that automatic category navigation, and you see results in all categories. In that case you will have to change the category yourself if you just want paper money.
Here is the same search, with the exclusion, in the Paper Money: US category:
https://www.ebay.com/sch/3412/i.html?_from=R40&_nkw=%242+bill+-colorized&LH_TitleDesc=0
And here is a search using dollar -colorized and also using the $2 denomination filter:
https://www.ebay.com/sch/i.html?_from=R403&_nkw=dollar+-colorized&_sacat=3412&LH_TitleDesc=0&Denomin...
