Average job value is revenue divided by jobs. Raising it produces more revenue from the same number of customers, which is why it is generally cheaper than winning more of them: the enquiry has already been paid for.
Scope
Work found and quoted while already on site costs nothing to acquire. The travel, the visit and the diagnosis are already spent.
This is why a business with a strong technician-level habit of noticing adjacent work has a materially higher average than one without, at the same prices.
Options rather than a single figure
Presenting a good, better and best version of the work rather than one price tends to raise the average, because it moves the decision from whether to buy to which to buy.
It also stops the business from choosing for the customer, which is what a single mid-range figure does.
Bundling
Combining related work at a package price raises the value of the job while giving the customer a reason to accept it. Margin has to be checked rather than assumed, because a bundle discount comes out of it — see job margin.
The mix of work accepted
Average job value also moves without any single job changing, simply by the balance of work shifting. A business taking on more installation and less small repair will see the average rise on its own.
Whether that is an improvement depends on margin. Larger jobs are not automatically better ones, and volume without profit is what happens when size is pursued for its own sake.
Recurring work
A maintenance agreement raises lifetime value rather than the value of a single job, and is worth counting separately for that reason. See building recurring revenue and customer lifetime value.