Let me start with the essential, fixed costs for building a sales funnel.
You'll definitely need web hosting, autoresponder, page builder, CRM software, payment processor and tracking software.
There are a few other pieces of software that can help you with Conversion Rate Optimization (CRO) that some would consider essential. But, you can add them once your funnel is built and/or profitable.
The prices of those items, depending on what you choose, also vary greatly.
However, a couple of companies provide integrated sales funnel solutions.
ClickFunnels provides hosting, autoresponder, Page Builder and CRM software. It's relatively easy to use and works with common payment processors. Expect to pay about $300/month. You can get like half off through this link.
It is probably the best choice for most business owners looking to profit from a sales funnel.
Most of the other choices are more expensive, time consuming to learn and not as effective.
There is one lower cost alternative but it takes a bit more to setup and is not as full featured as ClickFunnels.
It's an offer from a web hosting company called Insty.me.
They offer great hosting (I've used them for almost three years without issue), an autoresponder service, Page Builder and a few other marketing tools and resources. It doesn't offer CRM, integrated payment processing or tracking but you can add Google Analytics and still use a reputable payment processor.
Once your funnel is profitable, upgrade to ClickFunnels.
Insty.me currently has a Free Trial Offer with the Page Builder included, for just $1.
As for the non-essential, nice to have fixed costs, I'll choose not to discuss so as not to confuse you. Other than to say, most are very expensive; but worth the money when you want to squeak out every bit of income possible.