That will be based upon 5% page coverage - in basic terms a letter. There are programs that analyse toner coverage of a document available online mate, and it can quickly make you see that 7000 can soon become 1000 actual pages (unless of course you only print letters)
I shat myself when I got through a full set of 4 colour toners printing just 300 leaflets (my toners are quoted at around 2000 pages each). When I analysed the leaflet I was printing, it totalled 367% toner coverage. Obviously that's due to a certain percentage of each colour, but even with a mono laser I bet you will frequently print stuff out that has a 30% or more toner coverage.
Getting away from all that negativity though, I wouldn't be without it now. They just keep on rolling out the prints and never give you the jip that most inkjets do. I just try to keep it for essential printing now, paperwork / invoices / kids homework etc. If I need leaflets I order them in as it's far cheaper anyway for large quantities.