I bought some loose diamonds online to supplement Mrs. RoG's store bought ring. I had a jeweler friend modify her ring and mount the stones I bought next to the larger stone that came with the ring. Total cost for everything was under $2k I think (maybe closer to $1500?). I paid $75 to my buddy the jeweler for the goldsmithing. Retail is probably $100-150 in my area. Double it if you're in a high COL area (or drive to chinatown or somewhere that has less expensive craftsmen).
Right now, we're not really sure where the ring is. Probably in the box with tons of 24k gold jewelry. Unfortunately it's nowhere near as valuable as the 24k jewelry. Diamond was non-negotiable for her at the time, but 11 years later, she's probably changed her mind.
I paid 2 weeks salary from my summer internship at a law firm. Screw that 2 months salary crap. Or is it 3 months now?
My advice would be to get realistic with your bride to be on what the diamond means and what parameters you should use to choose what you're buying. I remember we focused a lot on the 3 C's (or are there 4?) cut, color, clarity and ?? None of your wife's friends are going to know jackshit about any of those things. None will ever have a jeweler's loop to check for microscopic defects. If the bling looks pretty and is big and fat with no massive imperfections, then that's all that really matters. I'd suggest skimping on every non-size related aspect of the diamond to get the price down as low as possible if you absolutely must purchase a 2 carat piece of crystallized carbon.
But seriously, I probably wouldn't marry a person that insists on spending that much on a ring. That's almost what we spend in an entire year including vacations, replacement funds for the house and car, etc. What are the odds that there will be wedding, honeymoon, new car, new house, etc demands placed on you based on what similar earning peers purchase? You, sir, might consider a $25k ring very inexpensive in hindsight. I would much rather blow $25k on a trip around the world, or even buy a nice used luxury car (if I'm trying to waste $25k).