Is it possible to convert my Stack Overflow reputation into dollars (or better in euro)? It would be nice to see a service which allows it (not to say it will encourage people to spend their time more productively).
Step 1: Earn a reputation on Stack Overflow.
Step 2: Head over to Stack Overflow Careers.
Step 3: Get an awesome new job after showing off your skills.
Step 4: Profit!
There is likely a market for 10k+ accounts, but it's liable to be small. I expect that, at a minimum, a good programmer could rep-mine an account to 10k in about 2 months with about 2 hours a day. 120 hours of a 'good' programmer's time represents a value of around $10,000, or about $1 per rep point. The reverse isn't necessarily true (ie, 1 vote = 10 rep != $10, but the proof is left as an exercise to the reader).
However, there are likely to be very, very few people willing to pay anywhere near that amount for a 10k account.
Further, if the Stack Overflow team learned of such transactions (which, with over 100,000 users, must certainly have already taken place) then it is likely that they would consider locking the account.
Rep is meant to be a reflection of the person's stance among their peers, and transferring rep, except for bounty questions, is not part of the system for that reason.
So yes - it is possible. It's not liable to net you anywhere near the value of the time you put in getting that rep, and should the transaction be detected you may have an angry buyer to contend with, as well as losing your account.
Well, if you can find anyone willing to pay for an SO account with lots of rep, then yeah. But I don't think you'll have much luck finding a buyer.
Edit: Especially not for 443 rep.
Put your stackoverflow userpage URL on your resume or business card, so that others can see how much you know.