Of course doing it myself isn't free. First there is the cost of the clippers. I have 2 sets, the large for the body and smaller for the legs, face, ears, and whiskers.
The smaller one I use, the Oster A5 runs about $140.
Now these pictures are much newer models than the ones I own. Total
purchase price of $410 seems like a lot for clippers but I have had my set since about 1998. They have more than paid for themselves. I keep mine clean and serviced regularly so I may even get a couple more years out of them. The A5s are a tad tired though.
As far as other costs a set of blades for the body clippers run $30. If you keep them clean and only clip clean horses a set will last a few clip jobs. I keep size 10 blades for legs and face for the A5 and size 40 blades for ears and muzzle. Those run about $25-$30. Oil runs $3, blade wash $7 and Kool Lube $8. The cleaner you keep the blades the longer they last. You can also get them sharpened for $5 a blade versus purchasing brand new.
Time has a cost too. It takes me an hour to clip a well behaved horse. If you have a not so good one add in the cost of Ace (sleepy med) and longer time. Hobbs used to be really ticklish (I say used to because now in his old age he is much more tolerant) and he used to take me 2 hours.
If you have multiple horses, a lot of patience, or simply love clipping it is worth doing it yourself. My clippers have long paid for themselves and with multiple horses to clip, it's a great way for me to save money to put towards horse shows. To learn simply takes practice and learning some tips from others with experience. Practice on some lesson horses or something not going to a show a few times and it's easy to get the hang of.