My fiancee and I have combined finances where we pay all bills from, as well as our dedicated combined savings goals (house downpayment, taxable investing, IRAs etc)
We do fun money into our former individual personal accounts based on our income, (both high earners, but she between 50-70% more).
I get $100 per paycheck, and she gets ~$165 or so.
So that's $216 / month for me and $357 / month for her (we're paid bi-weekly)
What we consider our 'individual fun money' is ANYTHING we spend without the other one being present. Drinks with co-workers, work lunches or eating out separately, video games, computer parts, clothes / makeup / accessories, whatever else.
Those amounts seem pretty lavish when put into perspective here, and we've found that we're saving more fun money than we're spending, so we may either dial it down in the future or just let it amass and have a discussion on whether we want to roll some of it toward our downpayment fund, or combine it toward a vacation etc)