if you mean this one it's not such a fabulous deal.
i'm assuming you're buying for a newbie, of course, as most hardcore or experienced cachers would probably have a unit by now. you can find the etrex 10 on amazon for 94.75 and if you have amazon prime it ships free. i have the camelizer plug-in and it looks like the unit was $119 in july but it's been coming down ever since. given the rotation of products, i'm not sure i expect to see that unit price rise again after new year's.
the groupon deal is the same unit rounded up to $95, and as a bonus you get a cache container and some small goods.
now if your newbie gift recipient is really enthusiastic about getting into geocaching, it could make a nice little bundle. you're basically getting some accessories and their first cache container thrown in for free. those accessories and the cache container aren't hard to come by and usually aren't expensive anyway.
it's a nice gift idea in that you get the unit and some other items that makes it look like a really lovely bundle of stuff. but purely speaking from a price perspective it's not much of a deal.
They're going for $90 new on Amazon currently so it's not too bad. I scored one on eBay for about $20 a few months back and that was a steal of a deal so $50 is not too bad in my estimate.
That's because it's an aviation GPS function, not just something you "buy" on Amazon.
This is complete BS and it literally is