More important than the commission will be negotiating all the other clausules (involvement, support, time period, exclusivity...)

In other sector (Cloud IaaS) I've been offered all kind of offers raging from 5% to 50%.

It will always depend of what this insider will do for you. If she is really good, only makes introductions and "helps" during negotiations, I won't pay more than 10% (per my experience in my sector, yours would be different).