Is my HOA figuring the association dues correctly?

I own a commercial condo in a mixed use complex containing five (5) commercial units and four (4) residential units. My condo is a commercial warehouse space with 20' ceilings and two garage doors. The other commercial spaces are finished retail. The residences are very high-end condos. One of the units sold for $950,000 in 2008. When I purchased my unit (new construction), the building owner had the HOA fees determined by overall square footage. My space is 2600 square feet, or 25% of the total mixed-use project (inside footprints). Therefore, I pay 25% of the entire annual budget for the HOA. I feel this is not a fair way to allocate the fees, and should be divided equally by the total number of units, or have equal fees for the commercial units and equal for the residential units. How are other mixed use complexes figuring their association fees? Thanks, Roger