If you search for exact match results (with quotes) you actually only get 7,340 results - many of them not intending to have the words together as a keyword phrase. Also, 0 exact match searches per month on Google as well. To be honest, it doesn't make a lot of sense in English to me... Does it mean where you pay to play slots? If so, that's not normally how someone would word it and why would somebody be looking for a site where they have to pay? It would be more likely to see a site where they can gamble/make money (which would usually require you to pay, but that wouldn't be the focus of the search). Gambling domains can sell well, but I don't really see the value here as is I'd put it at regfee low $xx enduser and mid - high $xx enduser. Development would be your best approach, but then I would look for a better domain to develop than that personally. There is a reason you found this at reg fee.
Hope this helps!