not sure what GPN gets for a private gig - but I'm guessing it would be around  5-10k, more or less. I know a few years ago the Radiators charged 6500 for a private party, a little indication of what bands charge for private parties.

this from a quick google search - 
On average, US couples spend $20,398 for their wedding. However, the majority of couples spend between $15,299 and $25,498 while their wedding budget is typically 50% less than the amount spent. This does not include cost for a honeymoon or engagement ring.

if you consider you could skip a fancy reception and have a more modest one  and  have GPN play - why would there be any question as to which creates a better memory?

Laissez les bons temps rouler!