And I personally don't see the point of paying an additional $40 for 3G connectivity on the iPad that I'll never use when I already have 4G/LTE connectivity that's about ten times faster via a mobile hotspot or a tethered 4G phone.
You'll note that the OP indicated he/she has a "wifi iPad." Purchasing a bluetooth receiver makes much more sense than selling the iPad at a loss and then spending an additional $130 to get GPS functionality.
There's no question that if one needs built-in 3G connectivity on the iPad and don't need the superior GPS functionality provided by a dedicated GPS receiver, the $130 (USD) price difference is a reasonable expense. If you're not in either of those camps, however, a bluetooth GPS receiver is an excellent alternative.