Materia price went down to dramatic low amounts for instance too, a tons of things did.
I play on low-pop server and i used to make quite a big money on materia alone and materials for tomestones, after they introduced server visiting everything went down and so my income from around 5 mil a week went to under 1 mil.
Price of the equipment barely changed mate, it was the materials and other stuff that is being sold mainly got giant price drop to the floor. Newer players and poor players and average players have it 10 times worse to earn gil than before and i speak here out on my experience. I was able to just resell a lot of vendor stuff for profit, because everyone had gil to spend and it was running through the market in much bigger quantities than now. Can you sell stuff from vendor for profit now? I doubt.
When i started playing on Zodiark people were buying paint from me because they could afford it, now they dont because every gil is much more valuable and harder to get...
No, there is no system that will fix it.
Just block selling options for those that are business-visiting, because they take all the stuff from twice or three times as big markets and bring them to small ones completely destroying any balance. 50 of guys like this and price drop like crazy, because they are flooding market with goods that this market just cannot buy.
Low prices casued by flood of supply doesnt benefit anyone, it makes it harder to make any gil at all.
Server visiting makes it easier to manage RMT, its should be restricted heavily.