It is better to be contented over something than to have nothing at all.

Alternative form of there is nothing new under the sun

plural of nothing-up-my-sleeve number

(cryptography) A number which, by its construction, is above suspicion of having hidden properties; used in creating cryptographic functions such as hashes and ciphers.

Alternative form of you don't get something for nothing

One cannot expect to receive some benefit if one does not pay for it in some way or does not face a counterbalancing hazard or harm.

Alternative form of there is nothing new under the sun