Sure. You could probably order 1000 pounds of fertilizer online today too. Just don't be surprised if you wake up to a search warrant.
That's looking at things the wrong way though. A runner doesn't buy a lump sum of reagents online; a talismonger contact of their's buys the reagents, which isn't strange. Then they buy from the talismonger with an untraceable credstick, and the talismonger just makes it look (in his records) like he sold that many throughout the day, having a really good day of sales. What's a questionable amount for one person is a lot less questionable for five people who just needed a lot for their big plans (like a major ritual or a marathon of binding spirits).
Or you're getting it directly from an illegal talislegger and there's just no records at all; though in this case you wouldn't be able to get them all right away if you ask for more than the talislegger has. But if they're making any kind of profit, they would probably need to getting a whole lot.