In the long run, yes decreased cost results in decreased prices TO THE EXTENT THAT COMPETITION IS ALLOWED.
If, say Cricket wireless can provide the same service at half the cost, they'll charge less in order to get market share. On the macro level, it puts downward pressure on prices.
Here's a concrete example for you. In the web hosting business, like many others, 20% of the customers result in 80% of the cost. Most customers never require much attention, the servers just run, the bill goes out, and their credit card is charged. A few customers run opt-in mailing lists, and while those are legitimate, they cause some spam complaints that needed to be handled, they need DKIM set up, etc. Other customers feel they need to install a new script every week, so they need a lot of support, and since they do everything ad-hoc rather than settling into a pattern they miss paying their bull sometimes and you have to call them a couple of times to get them to pay. Many years ago, I started a very small invitation-only web hosting service. We only hostprofessional webmasters who know what they are doing, so they don't bug support with stupid questions. Their invoice is billed to their business credit card every month. I have customers I haven't heard from in years. Because of this, our costs are low, and so are our prices. We can provide excellent service at an excellent price because we're not spending our time and money dealing with spam and DMCA complaints, or chasing down past-due accounts. Our costs are low, therefore our prices are low.
* no, we won't host your site. Not unless we know you, or people we know vouch for you. We don't want new customers unless we know those new customers won't bring DMCA, spam, billing, or support problems.