I started to write a reply but when the pop up ad with a picture of Hillary came up on my screen, it made me ill and I had to stop to clean my keyboard...
Sorry, off topic. But you should have warned me about pornography on this website.
We had our current ERP product customized by 3rd party. One day, that group went away and was eventually purchased by the ERP manufacturer themselves.
Due to our customizations, we could no longer get the updates/upgrades as they came out because of the unknown effect of the customizations. Our 3rd party vendor would first test those and then send us the update and any modifications needed. Worked well as updates only came out once or twice a year. Some of those same customizations that we developed later became incorporated in newer versions. Since we could not get the required support, we dropped paying the annual maintenance and have been trapped in a now older version with no upgrade path available.
So in this case, both the build and buy options were used and both came out bad in the long run. It did work very well in the beginning and was a cost effective solution. Building from scratch was not in the budget.
The problem is now resolving itself due to a buyout of our business and we are being forced to use their existing software, which is 10 years old, text based and runs on a Unix system. No more SQL.
Down the road, the larger parent is now developing a new CRM product which will be Oracle based.
Here we go again.