My experience is not aplicable for you, but for me with my husband it looks like this.
Last time he got visa was after our marriage (4 years ago), after that we apply every year for temporary resident card, and it costs us less than 2000 UAH (state fees+notary translation+insurance). There's no possibility for corruption. In february 2020 we applied for permission to immigrate (and it was same with all payments legal) after which we will be able to get permanent resident card. But we can see on the migration office website that we have allready this permission, and it will be sent to us by post. 2 months passed and I am afraid that I need to search this document I do not know how. Before Covid it was quicker and easier as far as I know from my husband's friends, but now we are waiting more than one year.
And after that same permission to immigrate my husband will just need to study ukrainian language for citizenship, but it's not urgent after permanent residence.

If any third party tells you about corruption then it can be cheating for extra money or it can be extra payment to any party involved, and they explain it like this (e.g. they need to pay to fake husband, or college documents where you will not need to study, or company invitation where you will not work).

But I agree that it's very different depending on the country since my husband can come to Ukraine without visa any time for 3 months, and we got the visa just for the purpose of residence.