It depends:
-I've shown a "professional installer" the door when he didn't appear to have a clue.
-I left a VOOM installer $50 because he did a neat job, property grounded the dish, and ran the RG-6 into the basement where I asked him to (80 ft. run vice 25 ft. to drill through the side of the house)...of course, I also ran RG-6 to both TV locations prior to his arrival.
I was going to give the VOOM installer $25 for running out an additional receiver (installation). I ran the new RG-6 to a wall-plate, connected it to the switch, and made two 4 ft. sections of RG-6 to connect the receiver (satellite and OTA ports) using my compression tool and fittings. However, when I realized I had forgotten to make a 4 ft. length of RG-6 w/fittings for my OTA A/B switch, he replied that he would have to charge me $5 for the cable and two fittings. Needless to say, I pulled the $25 out of my pocket and had lunch at a local steak house instead of giving it to the douchbag. I should have made him reimburse me for my 58 ft. of cable and 6 fittings.
Finally, I gave the Dish Network installer $60 because he was an excellent communicator and did a very tidy job installing a two-dish 500 system, 4-tuner system. He appreciated the fact I ran all the cabling, and installed the switch in the basement exatly where I wanted it. He was in and out in about an hour and told that he wished all customer were like me. I told him I wished all installers were like him.