Well one thing an OTS solution accomplishes is it makes costs and capabilities very clear to product and marketing. When you have an internal team doing something bespoke to your organization it is viewed as much more malleable.
If the third party solution cannot support the billing system devised, or will support it for a large cost, companies are more likely to choose things that are more in the box.
Except with many of these enterprise solutions (SAP, Netsuite, Salesforce) most companies will still need to pay consultants 300 dollars an hour to configure and maintain the application. These costs often exceed the license cost itself.
Bottom line, complexity is expense regardless if you build or buy. Companies need to factor the systems and operations impact of complicated pricing and billing models into the decision making process.
The absolute cost isn't important here. What's important is that cost is now explicitly on the balance sheet were someone can see it. If you have an in-house system, that team is treated as an infinite supply of features for no apparent cost. (Ask me how I know.)
And as a developer, I love being able to hand certain people over to vendors who are used to dealing with those certain people. Hell, if we picked the right system, those vendors will have useful domain knowledge I don't have.
That is not the case in practice. Those AAA vendors will ask you, the customer, for all the domain knowledge in a very expensive 'configuration project', and shuffle many of your specifications into a bespoke 'customization and integration project'.
> Well one thing an OTS solution accomplishes is it makes costs and capabilities very clear to product and marketing.
It gives that illusion. The reality is not so clear cut. There are lots of nuances to a capability that's not just a box check. It could be half-done, i.e. certain bugs in certain scenarios. It could be slow, unreliable or something else altogether.
If the third party solution cannot support the billing system devised, or will support it for a large cost, companies are more likely to choose things that are more in the box.