Assuming that blade is less than 4 feet long, sure. Longsword blades would work, just be sure to package them carefully so you don't spill all your good onto the astral plane as you said.

But if we assume each blade is in a 3 inch square sheath (it's actually wider than deep, but I don't want to do that math), you get 64 blades in a bag. You don't get anywhere near 250 blades because of the bulk that you're ignoring. Not that most people pay attention to the details, mind you. Of course you could put them all into a single container for shipping ... hmm.
Let's just say I'm not convinced you could get 250 blades in there but I'm too lazy and not good enough at the math off the top of my head to figure out the actual number. More importantly how often are you you would regularly shipping that many blades to one destination for direct sale? These are naked blades, not the finished product, no crosspiece because that would increase the bulk dramatically so they still need that work done before sale to the final customer. Sending to a retailer to split up and redistribute? Sure. But then you're not getting anything near retail price for a sword because they have to finish assembly, store the goods, then ship off to multiple locations where using a bag of holding becomes less worthwhile.
On the other hand, using a completely random object, a real world longbow wouldn't fit. So how many valuable trade goods would fit? But yes, for certain goods it may be worthwhile. What percentage of goods is that? It may worth it to a merchant trading in other high quality goods where you can fit multiple into the bag. The majority of goods that would fit in a bag of holding are not that expensive per pound or are too large to fit in the bag.
All of which doesn't account for supply, demand and the impact of lower shipping costs. Spice prices were inflated because of shipping costs, but if it's as easy as stuffing a bag of holding full then the supply increases dramatically which deflates the cost which drops the profit margin. Since I don't have a masters degree in economics I'll just say that it would be complicated.