Consider supporting not only what the software is going to require but the supporting vehicle architecture inside as well as outside the vehicle. There are costs associated with making sure that you have the data transmission requirements needed in order to capture the data out of the car and then push more information to the vehicle.
If you're trying to bring a vehicle to market at a certain timeframe, your platform might not be ready by the time the vehicle needs to be launched, which could incur further costs, especially if you must delay the launch of the vehicle as a result.
It’s vital that there is an understanding of how to integrate the Electronic Control Units (ECUs) that you want to have access to so that every part of the vehicle can have OTA updating capabilities. It's a challenge to build an architecture that way and there's different technologies that come into play both onboard and off-board that in many ways are new to the industry.
If an OEM builds out its own OTA platform, the pros and cons can range from owning the IP and being as profitable in this area as the whole connected car architecture is. However, it's likely going to take a lot longer to bring it to market. There is a risk of having the market shift underneath you while you're trying to build a certain platform, which is going to take a lot of time.
On the opposite side of the equation, taking a partner approach leads to the shortest time to market. You're going to have to understand how your partnership is going to work and if you're going to 1) drive a system based off a pure external party software, or 2) if you are going to partner to design a software that works well for both of you.
By buying an OTA solution, you are increasing the experience and market insights provided by a provider who consistently works to bring this type of service to the marketplace. There is also the added benefit of obtaining new capabilities and features planned in the product roadmap through scheduled new releases. Customization for each OEM can create a challenge for the supplier of that software or those platforms and then of course, you will need to add in the cost of licensing the platform itself.