It's not CP3 or PG13 though.
It's a starting lineup of CP3, Green, Kawhi, Aldridge and Gasol or
Parker, PG13, Kawhi, Bertans and Gasol.
You lose Green and Aldridge most likely to trade for George. Theoretically they would only have to lose Parker to add CP3.
It's a team sport, the Spurs would have to gut their team for George, whereas they could get CP3 without giving up much at all.
They have to get rid of parts to get the cap space for Chris. Also it was just announced the cap came in lower. Either way you're going to have to lose pieces and I rather have Paul George and lose Aldridge. Sorry I think you're under estimating what they're going to have to do to be able to sign Chris Paul.