“Self-publishing, another option, is quite expensive since you have to pay for it to be done, whereas VDM does the whole thing for free. Those seem to be the main issues.”
If you check in Amazon, you will see that heir books sell at an extortionate price, something like 100 dollars on average, whereas other self-published books (in normal services where you have to pay a fee) sell for like a tenthj of the price. Basically, no one will buy your book and you are taking part in a scam. So, yes, you are happy with that, go ahead.