That to me is definitely excessive. Unless of course he's filthy rich, which would still make it excessive and unnecessary, but it's all relative.
Also, you don't want to get to that point where the ring is so expensive you're actually scared to wear it out. Kind of takes away from the whole wear it proudly thing. Turns more to wear it in fear lol.
On a side note, I've heard of the 3 month rule before, but I don't really agree with it. Seems a bit much if you ask me, especially if you earned a reasonable sum. I'd say two months was perhaps more fair. Bare in mind, as much as a ring is for a lifetime, so's marriage itself. And it's not exactly a picknick. Honeymoon, living, expenses, bills, rent, mortgage, outings, gifts etc etc. All things that will take a heavy burden on your wallet and must also be considered for the entirety of your marriage, especially the first few years where it might be beneficial to enjoy yourselves a bit.
Thanks dude, appreciate it