Cooper GFCI receptacle linked to above is $26.67. Siemens 20 amp Single Pole GFCI breaker is $46.97. Cheapest I saw was about $44 and they go way up from there.
I think the GFCI breakers are more reliable, if for no other reason than they are installed in a panelboard that is reasonably clean and dry. Receptacle should be also, but more likely to not be. Don't forget to add in possible additional wire to install the blank face GFCI in a suitable location, the cost of a box, and the additional labor or hassle of installation. GFCI breaker is rather easy in comparison.
Charles