I got bit by their pricing UI design that looks similar to many other sites, but is different in a way that caused me to spend far more money than I expected.
I'm writing this post so that you won't make the same mistake I did. As a product, DataDog is of course a lot of hard work to create, and they can try to charge whatever they want. However, my problem is that what they are going to charge was confusing and misleading to me.
I wanted to see some nice web-based data about my new autoscaled Kubernetes cluster, so I looked around at options. DataDog looked like a new and awesomely-priced service for seeing live logging. And when I looked (not carefully enough) at the pricing, it looked like only $15/month to monitor a bunch of machines. I'm naive about the cost of cloud monitoring -- I've been using Stackdriver on Google cloud platform for years, which is completely free (for now, though that will change), and I've also used self hosted open solutions, and some quite nice solutions I've written myself. So my expectations were way out of whack.
Ever busy, I signed up for the "$15/month plan":
One of the people on my team spent a little time and installed datadog on all the VM's in our cluster, and also made DataDog automatically start running on any nodes in our Kubernetes cluster. That's a lot of machines.
Today I got the first monthly bill, which is for the month that just happened. The cost was $639.19 USD charged to my credit card. I was really confused for a while, wondering if I had bought a year subscription.
After a while I realized that the cost is per host! When I looked at the pricing page the first time, I had just saw in big letters "$15", and "$18 month-to-month" and "up to 500 hosts". I completely missed the "Per Host" line, because I was so naive that I didn't think the price could possibly be that high.
I tried immediately to delete my credit card and cancel my plan, but the "Remove Card" button is greyed out, and it says you can "modify your subscription by contacting us at firstname.lastname@example.org":
So I wrote to email@example.com:
Dear Datadog, Everybody on my team was completely mislead by your horrible pricing description. Please cancel the subscription for wstein immediately and remove my credit card from your system. This is the first time I've wasted this much money by being misled by a website in my life. I'm also very unhappy that I can't delete my credit card or cancel my subscription via your website. It's like one more stripe API call to remove the credit card (I know -- I implemented this same feature for my site).
And they responded:
Thanks for reaching out. If you'd like to cancel your Datadog subscription, you're able to do so by going into the platform under 'Plan and Usage' and choose the option downgrade to 'Lite', that will insure your credit card will not be charged in the future. Please be sure to reduce your host count down to the (5) allowed under the 'Lite' plan - those are the maximum allowed for the free plan. Also, please note you'll be charged for the hosts monitored through this month. Please take a look at our billing FAQ.
They were right -- I was able to uninstall the daemons, downgrade to Lite, remove my card, etc. all through the website without manual intervention.
When people have been confused with billing for my site, I have apologized, immediately refunded their money, and opened a ticket to make the UI clearer. DataDog didn't do any of that.
I wish DataDog would at least clearly state that when you use their service you are potentially on the hook for an arbitrarily large charge for any month. Yes, if they had made that clear, they wouldn't have had me as a customer, so they are not incentivized to do so.
A fool and their money are soon parted. I hope this post reduces the chances you'll be a fool like me. If you chose to use DataDog, and their monitoring tools are very impressive, I hope you'll be aware of the cost.
On Hacker News somebody asked: "How could their pricing page be clearer? It says per host in fairly large letters underneath it. I'm asking because I will be designing a similar page soon (that's also billed per host) and I'd like to avoid the same mistakes." My answer:
[EDIT: This pricing page by the top poster in this thread is way better than I suggest below -- https://www.serverdensity.com/pricing/]
1. VERY clearly state that when you sign up for the service, then you are on the hook for up to $18*500 = $9000 + tax in charges for any month. Even Google compute engine (and Amazon) don't create such a trap, and have a clear explicit quota increase process.
2. Instead of "HUGE $15" newline "(small light) per host", put "HUGE $18 per host" all on the same line. It would easily fit. I don't even know how the $15/host datadog discount could ever really work, given that the number of hosts might constantly change and there is no prepayment.
3. Inform users clearly in the UI at any time how much they are going to owe for that month (so far), rather than surprising them at the end. Again, Google Cloud Platform has a very clear running total in their billing section, and any time you create a new VM it gives the exact amount that VM will cost per month.
4. If one works with a team, 3 is especially important. The reason that I had monitors on 50+ machines is that another person working on the project, who never looked at pricing or anything, just thought -- he I'll just set this up everywhere. He had no idea there was a per-machine fee.