My last community charged every house the same price 320€ per year up from 200€ over a period of ten years, which to me is only fair and correct, a large Villa didn't use anymore of the community services then i did with a slightly smaller Villa, the pathway lighting was the same for everyone, the pool was the same for everyone, i cant see just because you got a bigger sized plot you used more of the collective services.
Our charges went up the same for every house accordingly to what had to be spent on any repairs etc, when the pool wanted to be repaired due to lose tiles the extra full cost was divided up by every house, by a one of payment, and that was your share to pay, which we did.
I think what your actually saying is that the largest Villa's are paying the most charges, and if they (Charges) were all the same the smaller ones get an increase, but again what do the larger one's use more of then the smaller one's.
If you haven't had any increase in 6 years that can surely only mean one of a couple of things, either your community is very well maintained that no major repairs are needed or your fee's cover any expenditure not worthy of the mention.