There technically is, but profits are slim. It's why nowadays PC services are so much more expensive, because it's the only way shops can sustain themselves.
If you worked in a larger company like PC Specialist, you'll lose all love for it as it's not the same.
Hate to be the downer on this, but it's incredibly difficult nowdays, and typically it's the services that people pay for.
The people who aren't comfortable building a PC will often just go to a big name who can get cheaper products through contractual agreements, or will buy one off the shelf, and the others just build them themselves.