Depending on your golf shop, the cost for fitting can vary-- some fitting options are more sophisticated than others. In my experience, I attended a demo day and worked with a fitter-- which did not have a cost. If you look up fitting days on Titleist's website, a list of different events should be listed for the area you live in. Also, if you decide to attend a demo day, make sure to call ahead and make a reservation. 

In terms of discounts, it is unlikely you will receive one on your wedges whether or not you are willing to buy on the spot. 

I hope this helps. 

Buying some off the rack and getting lie checked shouldn't cost to get adjusted and probably won't be discounted.  Getting fitted to match shaft to your swing and lofts to be consistent to your irons and general course needs will have a fee and will be usually be discounted/dropped with a purchase.  Advanced fitters, pro shops, and big box stores will have different fees.  Wedges would be best fitted on turf.