I do miss the days when our bus fleet's were so varied and
filled with many different models. However, in this cost-efficient
world it's probably just better to consistently large batches of
one model.
Yes, having the same model in large quantity is more cost
effective.
This is called "economies of scale".
When the order is large, Manufacturers and Advertising companies
usually offer substantial discounts, as producing in large
quantities lowers the unit cost of production. This enables the bus
company to procure the products and services at lower prices, and
as a result, they are able to generate higher revenue.
When there are only a few models, Technicians can become
specialised in handling the buses. As they become specialised, they
tend to make less mistakes, and thus productivity increases.
With higher revenue and productivity, banks and financial
institutions would be more willing to provide financial support to
the bus company, at lower rates.
^^ Which is why Go-Ahead only wants B9TLs and Citaros, and they
outsource the advertising to Moove media.
However, the lack of communication and coordination in the very
beginning worked against them.
Hopefully, things are better now, because there are indeed
economies of scale to be reaped from Go-Ahead's way of operating
and managing the bus services.