Exactly. For example, we were told that my spouse could work while here on a 457 visa. That sounds to me like she can go get a job, like anyone else. But guess what ? Aussie employers always ask for the applicant's residency status, and those on 457s can only be hired if no equivalent Aussies or PRs are available. So in actuality, your spouse pretty much has to find a 457 sponsor just like you did, just like any foreigner has to.
Employers natuirally paint a rosy picture of work and conditions here in Oz - and let's face it, that's not difficult to achieve. But be warned ! All it takes is for your employer to finish a contract and need to drop headcount....and if you're a 457 in a department of Aussies, you're automatically closest to the door. Especially if the Aussies are all mates. Then all of a sudden it's cheers mate see ya and you have 90 days to find another sponsor or leave the country. Obviously this is less of an issue for those with widely-employed skills (tradies etc), but for those of us who are specialised, it can be a huge issue. People being asked to come here on a 457 may well be giving up a permanent position to make the move. It's only right that they are given the full picture as to just how temporary a position they may be getting in exchange.
I know people who have demanded PR upfront, or a commitment to sponsorship for PR after 2 years. If you feel you may have enough clout to swing it, give it serious consideration.
I post this message with the intention of warning and helping others.