Some people become entrepreneurs because they want to make loads of money. Others do it for the freedom and lifestyle it affords them. It just depends on what your priorities are. Personally, I prefer setting my own hours over driving a BMW.
For me, a non-Retina 13" MacBook Pro with upgraded memory and SSD hard drive approaches the perfect machine. It's cost effective and blazingly fast. The extra cost associated with a Retina display isn't worth it to me, especially given the premium Apple charges for the SSD upgrade.