Never thought I would agree with “real-brisker”, but this is a really revolutionary thought…
Once you have an idea of what you are prepared to spend, ASK THE CHASAN what he would like in that price range.
Don’t just get some “standard” gift to be “yotzai”.
Maybe he doesn’t wear or want a watch.
Maybe he doesn’t wear or want cufflinks.
Maybe he already has a nice Shas.
ASK HIM.
And… If he comes back to you with something that’s not up YOUR alley, SO WHAT, the gift is for HIM, – NOT YOU!
It’s an easy way to score points with your new, soon-to-be son-in-law (and make him more amenable to coming to you for Shabbases and Yom Tovim! 😉