Economy is one powerful motive for camping, since after the initial outlay upon equipment, or through hiring it, the total expense can be far less than the cost of hotels.【since after不是固定搭配：而是分开的：since为连词引导原因状语从句，after为介词，与后面名词构成介词短语作后面句子时间状语】

备注(1) :since(因为/由于/既然)为连词，引导既定事实的原因状语从句：

备注(2):after the initial outlay upon equipment or through hiring it为介词短语作时间状语，修饰后面句子的谓语动词, the total expense can be far less than the cost of hotels为句子主语+谓语动词结构

以上整个句子语法结构分析如下

Economy【主语】// is【系动词】// one powerful motive【表语】// for camping【修饰表语后置定语】, since after the initial outlay upon equipment, or through hiring it, the total expense can be far less than the cost of hotels【原因状语从句，修饰主句谓语】.

原因状语从句语法结构分析如下

 since 【从属连词】//after the initial outlay upon equipment, or through hiring it【时间状语】//, the total expense【主语】// can be【谓语动词】// far less than the cost of hotels【表语】//

备注(1):less than 表示低于/少于

备注(2):far修饰比较级起强调作用，far less than 比..少的多

关于since作介词和连词结构用法如下

【1】since +单词/短语 为介词用法

She's been off work since Tuesday.星期二以来她一直没上班。

We've lived here since 1994.自1994年以来我们一直住在这里。

I haven't eaten since breakfast.早饭以后我还没吃过东西呢。

【2】since +完整“主语+谓语”结构的句子 为连词用法

It's twenty years since I've seen her.我已经二十年没见她了。

How long is it since we last went to the theater?我们多久没去看戏了？

I'm forever on a diet, since I put on weight easily.

我永远都在减肥，因为我很容易长胖。

We thought that, since we were in the area, we'd stop by and see them.

我们想，既然到了这个地方，就该顺便去看看他们。