SE just added a very expensive housing feature to the game, so currently there are a lot more players actively trying to make some money (rather than just letting it accumulate at a natural but rather slow pace), and at the same time a lot more players trying to save money so they're less willing to spend it just to save a little time. A lot more sellers + a lot fewer buyers = prices on everything are going to plummet.

It's not likely to change until the interest in housing wanes. Maybe once most of the groups actively saving for a house have gotten it, then competition might wane enough to get a bit more profit again (or possibly not if some other real use for gil is added by then).

The main reason you could make so much profit before was because people had gil which they had no real use for, so they were willing to spend it for even the most minor of conveniences. What we have now is actually a more healthy economy, but it's one in which profit will be a bit harder to come by.