Historically clean IP space has been sold from $8-$12/IP. A /16 is 65536 IPs. I guess if you have $700K sitting around you can go and get yourself a /16. Or if you have demonstrable need and operate in a region where the RIR still has IPs available (ARIN/ AFRINIC), you could you know, just get IPs via the normal channels.
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this amount of ip's will be really expensive and if you need this range in Europe (RIPE), you have no chance. ARIN is other story, but still - it will be really expensive. In Europe is possible to get smaller blocks, but /16 is really sweet dream....
In reality, there's no way you'd get away with a /16 RIR allocation today, at least nobody who's asking on a forum - you'd have to gradually increment your holding whilst showing that the IPs are being used reasonably and by the time you got to /16 on the /20s or /21s or whatever they'd be handing you at the most, the RIR would have exhausted their remaining allocation already.