I found two conflicting statements regarding the limit usage of google stati map api
According to this link, 25 000 usage limit are allowed per day
According to
The limits both apply. 25000 for your application, 1000 per user, as said by Mano Marks. But if I unterstand you right, you just want to link to a map? Why don't you just use a standard google maps link? Then you wouldn't have any limits.
And still, if you just link to the staticmaps call (e.g. this example), your application has nothing to do with the staticmap call - its the users decision to open it. I guess there won't be any limits for that. (But perhaps they DO track the referrer and apply the limit for your page.)