Lots of good points here, but the point keeps coming around that it's not worth the money, unless your business is firewood. We're assuming your business is tree work.
I have had great success in giving it away free, but this involves a strategy. If done right, your firewood finds a good home and you have unpaid assistance in getting it offsite.
The strategy begins with perfecting your art of making the firewood, which involves three critical, though easy-to-master details. First, flush-cut all laterals. If you leave weird stubs and odd protrusions the wood is harder to split, stacks funny and the bigger pieces won't roll. This makes the wood less appealing on the receiver's end.
Second, make sure all the pieces are cut 90 degrees to the direction of the limb. Weird angles make it so the piece won't stand up on end when being split, making it a major hassle, even with a hydraulic splitter.
Third, make consistent lengths. 16" is considered standard length, so set your intent to make them all standard. When diameters get bigger across than the standard length, it's harder to gauge. I have a scribe mark from the tip of my bar, 16" on down for quick reference. When you have big blocks to knock off something 30 or 36" across you tend to cut longer. In other words, longer looks shorter when the wood is wider. If you're cutting off 20" blocks, once split, these pieces won't stack well because they're too long with regards top the rest of the pile. Nobody at the splitting end wants to re-cut something you've already cut.
Attention to these details will not cost you that much extra time, and the quality and consistency of the firewood blocks is much more valuable to the end user. They are more likely to want firewood from you again in the future. You only need a handful of these guys on your call list and you will save yourself countless hours moving wood by hand. At the same time, cutting off humps and stubs and angled ends will add to the amount of chunkity chunks in the waste, but little pieces are your tradeoff for having someone gladly and happily move out your big blocks.
Note that in this approach, YOU are not the one splitting. You're just assuring that the firewood length pieces get moved off your jobsite swiftly, spontaneously and happily. If my guys have to come back for a third load, I'll give them a twenty for gas money. I express how important it is to me that they make money with the wood. You're on their side and dedicate yourself to their success. You can even help them market the wood; when your clients ask where to get split firewood, you pass along their name. This costs you nothing. YOUR money is in the time saved and being able to finish and move on to the next job.
This will 'save the back of a young buck' and is a win/win relationship, sustainable over time without the investment of money. It's easier to make a phone call than it is to load and haul tons of wood. You just have to commit to making good wood.