Reddit mentions of SE 7-1/2" Ice Tempered Stainless Steel Barber Scissors - SP105

Since your professor doesn't have a mustache he'd still need to shave, but I'll assume a full beard and just use him for beard length reference to make this a proper comparison.

If you trim your beard with scissors (which is how you'd do it at that length) you only need a set of scissors. You can get them for as little as $4,27 with free shipping and they should last you a lifetime, but for the sake of argument I'll assume a scissor gnome comes every 10 years and steals them so you have to get new ones. Assuming you maintain your beard from the age of 18 to the age of 78 years (life expectancy is actually 78,8-80 years, but this gives a round number) you will have to buy exactly six scissors and then croak just as you were on your way to get the seventh. This puts the cost so far at: 4,27 x 6 = $25,62. Since you have to maintain your beard you have to get shampoo to do it. I'll assume you use a large pack of Head and shoulders (since that's what I use) which goes for $9,84 for a liter bottle. That pretty much lasts at least two months (so six bottles a year) since that's about how long it lasts for me and I have relatively longer hair. I'm assuming that you don't have an enormous mane of hair to wash, but rather short hair, so that the main expense for shampoo is washing your beard. With that we have the cost of washing your beard at: 9,84 x 6 x 60 = $3.542,4.

This gives a grand total of $3.568,02 for a beard.

If you shave, you will presumably be doing so every day. Since I based the part above on the items I use, the same will be true here. For shaving gel (because it's so much better) you have to pay $3,17 for a bottle and it lasts for about the same time the shampoo does. So I need to spend 3,17 x 6 x 60 = $1.141,20. Now we come to the issue of razors. I personally use this one at a rate of one per year (but since I shave once or twice a week, because I'm lazy and go to an college with no women, I assume you'd spend at least three if you shaved daily, also I obviously buy razor cartridges as replacement). I will also assume you have to replace the handle for unknown reasons every 10 years. This means the total is 11,47 x 6 + 32,54 x (3 x 60 - 6) = $5.730,78. Now you'd also have the cost of aftershave to account for. Again I use this one and it lasts for around a year (I don't shave every day). I'll assume for the sake of argument it'd last everyone that long which gives: 6,97 x 60 = $418,2. This gives a grand total of $6.263,18. for shaving every day. This is almost twice what you'd spend on cutting your beard with scissors and conditioning.

Now you might say, but I don't use those shaving products, I use the cheapest brandless ones. Lets see how they hold up. The cheapest shaving gel listed was $2,74 for a bottle, and the cheapest razor were $0.20 a pop, while the cheapest aftershave went for $2,12 a bottle. I'm going to have to assume a much higher attrition rate for both razors and shaving cream, since they are of much crappier quality. I'm assuming you go through a razor a week and finish a can of shaving cream on a monthly basis. I'll leave the aftershave at the same level, even though in my experience aftershave gels last much shorter than proper aftershaves.
Plugging all of this in we get: 2,74 x 12 x 60 + 0,20 x 52 x 60 + 2,12 x 60 = $2.724 for cheap shaving. This is less than a beard, but now we have to see what if we use the cheapest shampoo.

Again the cheapest listing I got was $2,88 for 0,8 liters. Since it is 0,2 liters less than the previous one we'll multiply the number of purchases accordingly. I will also increase it further by additional +1 multiplier to account for the fact it's crappier at doing its job. This gives us: 4,27 x 6 + 2,88 x 2,2 x 6 x 60 = $2.306,58 for cheap haircare which is again less than shaving.

So in conclusion, if you use mid-range products for both shaving and hair care you can save almost 57% by not shaving, but if you're using lower end products you will be only marginally better not shaving due to hair care being more sensitive (damn dandruff) to the quality of the products used.

disclamer: I used Walmart and Amazon for prices since they're the most recognizable names I knew which sell these things and I guess most of you guys don't buy your stuff at a Croatian supermarket which is what I'd use normally.