Some other things to consider:
There are a lot of different things sales people do. For example, a different sales person might do any of the following:
1. Make the phone ring that you answer.
2. Answers the phone and convinces them to talk to you so you can close the deal.
3. Closes the deal and hands you an actual client.
4. Babysits top clients to keep them happy for years.
Each has a different value. You may give 2% to the person who made the phone ring, 5% to the next person, 10% to the next, for total of 17%, plus another 5% to the next person.
Those are random numbers. You need to figure out you can spend on sales and how much they will get over time.
If you give a straight percentage commission on products that have a long stick rate, eventually they will sell enough that they don't need to sell any more, and then your new leads dry up. So, you may need to put caps on commissions. Good sales people have a magical power. They can swoop in, make some sales, earn a lot of commissions, take a vacation for six months and repeat when they run out of cash. They are always in demand.
So, caps might look like 5% of the first 100k, 2.5% next 100k, 0.5% of rest.
And of course, there are junior people and senior people, and combinations of pay + commissions or straight commissions. For example, you might have a college kid who makes the phone ring for 1% with caps + $2k/monthly, and the senior guy who closes them for 10% commissions with caps.
Hope that helps,