The seen costs are smaller, but the unseen costs are much higher.
If you offshore your development, the cost for that would be lower. However, the product will not be to the specs you need or want, and the support department for the software will have an increased cost of supporting said product.
You will also lose customer satisfaction and customer references, which causes your business to grow slower than if you had complete control over your product.
This applies somewhat to inhouse applications. The increased cost of support, and crazy Sys Admin gymnastics needed to keep the application running will cause other issues. Possibly causing top talent to find a new job because of the idiotic software they had to deal with.