No the stores were run by the carriers. Sprint and Verizon had an App Store before the iPhone was introduced where they sold a third party J2ME apps. Those carriers took a 70% cut.
I suppose it might have been regional, but that was never the case here. You would just download the jars (or cabs) directly from the developer. The only cut would have been the ~2% credit card processing fee.
The source being the carriers shop and scummy online shops listed on newspapers getting paid via SMS codes, which one would need to pitch before they would even consider taking their royalties.
Well, I guess Symbian got N-Gage and the Ovi Store towards the end, but they never tried to lock it down against third party sources.