If you only have three titles, certainly it would be more cost effective to keep track of that data in a spreadsheet rather than pay $50 per year for a web-based product.
And you have more than three titles, it's going to end up costing you $100/$150/$250 per year just to have access to your own data. Surely it would be more cost-effective to simply set up a template in a spreadsheet and manage the data yourself. You don't have to have a "tangle of spreadsheets" if you just start out with a good, well-designed template. Even if you don't want to create one yourself, surely you could find someone to create one for you for a one-time fee rather than pay a monthly or annual fee.
What happens if the website is compromised? There's an awful lot of data in there that could be exposed, such as all your pen names and all your titles, performance history, etc.
I suppose I'm in the minority though. It seems these days, people say magic words like "cloud" and "any device" and other people are like "take my money, every month, yay!"