Sure, it is certainly possible to farm 300a with a 4020 and a 7000 planter why not take advantage of newer technology if it is available and has a good return on the investment?  I can still draw with pencils, velum and a T-square too...

Yes, it takes some initial investment but will return that investment and more in many ways, not the least of which is time.

Jim

edit: 100a of double crop beans x 30 bu/a x $14./bu = approx $42,000 gross income on the DC beans alone. If you take a newer bare bones 6r30 mounted planter with a life of maybe 10 years and if that newer planter produces maybe 5 bu/a more than the 7000  that planter will pay for itself very nicely.  

One reason for going mounted is they are much less expensive than a pull type as well as easier to follow the strip when planting corn.

jmho and experience. Use what you wish. Starting out, the 3010 or 4020 and AC planter is a way to get started with minimal investment. The OP here is in a different situation.