Flying is not a cheap hobby
But for VFR you don't need to update every month. Once a year is OK - same as the VFR charts are updated anyway.
One cannot compare aviation GPS with tomtom etc road nav. I have been driving with TT for years and while it is OK 95% of the time, the rest of the time it can be utter crap. TT buy in old road databases because they are a lot cheaper - about 3 years old. On the road, one gets away with it; it is just a nuisance when one enters a postcode for the University of Reading and it cannot find it