These two teams were able to totally take advantage of the cap situation before it recently exploded. I recently listed the Cavs salaries in another thread, but I will do so again here:
Lebron - $30.9M
Kyrie - $21.1M
Love - $17.6M
Thompson - $15.3
Kyrie, Love, and Thompson are signed through 2019-20 and even though they are basically 'maxed' out, they are really affordable contracts. Lebron could make $90M and that would probably still not be enough. Because of these relatively low salaries, they were able to sign Smith to $12.8M, Shumpert to $9.7M, and Frye to $7.8M - all signed for multiple years.
With GS, everybody knows about Curry's low salary and the cap increase allowing Durant to sign there. Their breakdown is this:
Durant - $26.5M
Thompson - $16.6M
Green - $15.3M
Curry - $12.1M
With Thompson and Green signed for multiple years (2 more and 3 more, respectively) at bargain contracts, they should be able to max out Durant and Curry without too much of an issue. They may choose to let Iguodala or Livingston go, but that is their own doing.
In comparison, if the Cs sign Hayward this offseason, they are looking at this from their two highest paid players:
Hayward - $30.3M
Horford - $27.7M
That is a combined $58M for two players who are good, but not Curry/Lebron good and this will be exacerbated greatly by the IT/Smart/Bradley expiring contracts next year.
tl;dr - Basically GS and CLE are super teams and they were able to build those teams using the old cap rules. Unfortunately for every other NBA team, this will not even out until 2020 or so. No worries, though, we have great young talent and a competitive team to watch right now. We may not win a championship without a LOT of injury luck, but it's still a good time to be a Cs fan.