Sure, if you're planning to service a large number of users, building your infrastructure in-house might be a bit overkill, as you'll need a infrastructure team to service it as well.
If you're just want to buy 4 GPUs to put in one server to run some training yourself, I don't think it's that much overkill. Especially considering you can recover much of the cost even after a year by selling much of the equipment you bought. Most of your losses will be costs for electricity and internet connection.
