Based upon the Draft Value Chart, the Patriots absolutely fleeced the Dolphins. The Patriots sent two 6ths and a 7th round pick to the Dolphins (the Patriots have roughly a million more) and now get to make a pick atop the 5th round. From a value perspective, the Patriots would have had to add an extra 6th round pick in order to make the trade fair.
Of course, the value of picks this late in the draft doesn't really matter. The Patriots don't have space for more players, while the Dolphins want to take as many shots as possible. A three-for-one deal helps both sides.
It will be interesting to see what the Patriots do in the 5th round. There are still plenty of top tier running backs available, which could be where the Patriots are looking to add depth.
The Patriots are now left with the following picks: #147, #208, #214, #221, #243