"But a gilded cage is still a cage"
"Like a bird in a gilded cage"
are both quite often seen as the idiom.
'Golden handcuffs' may be somewhat similar
(and the almost opposite of a golden handshake).
You may well have been unjustly fired, but you've been paid handsomely so you've got to keep schtum - the handcuffs may be golden but they're still handcuffs.
It's not a very common word in today's English. In Britain we do often refer to it as prison or jail, and most of the time it is spelt the same way as it is spoken. Gaol is more old English than the English that we commonly speak today. The pronunciation is much the same as jail though. In conversation the spelling of a word isn't quite as important as the pronunciation.
on Nov 11, 2017, they gave the translation as "but one prison is a prison" - but why not "but one prison is one prison" -- if one's uptight about having ANY prisons in one's city you could complain about having one already, with the risks / stigma attached, if they proposed having two -- like some US cities -- you could complain