Depends what you're fighting, but imo 300k an hour is probably an exaggeration because the primary events are more running than engaging. With the gameplay being so WS heavy (there's virtually no longer any long-term TP phase with TP bonus weapons and high multihit/STP builds now), you spend far less than you would think. Monk is the exception because it benefits a lot from TP overflow and can't use a TPB weapon. Most jobs fire their WS off within 2-4 seconds of a TP phase, which is like 3 attack round averages with Sam roll.
Gaol bosses are 15 minutes max, Segment farming is 30 minutes max with tons of running, Limbus is maybe 45 minutes? Which events are a full hour that you aren't running the majority of the time? Limbus is what I would consider the most expensive event of everything, if you were to use it.
However, let's assume it's spot on exactly how much it costs to run Hoxne for an hour. 300k average per hour. Is that supposed to be expensive? It's not like you pay it all at once, up front, like a food item you use with duration. You pay for what you swing. Unlike am item like gyudon+1, where you run for most of the event and then only get use out of whatever fighting you do, but paid for the entire duration. So it's not a true "you lose 300k for running Hoxne". Compare with something like meds, I pay 240k every refill of panaceas, which I mostly use a stack in a single Limbus climb. It's kind of on par with what other things cost. It's not unreasonable