I would suggest a price per square foot. You can include the price of the pavers or not depending on competition in your area. What to charge depends on your geographic area. In Florida, where prices are low, rates go as low as $2.25 per sqft for sand set installation. Other areas in New York and Virginia it could go as high as $25.00 per square foot. Huge difference. I would suggest analyzing the existing companies and what they charge very well, so you can offer a mid range price to gain market share. Good luck!
Pricing things per square foot is a good way to get off track real quick. Just because a few other companies charge $XX per sq. ft. doesn't necessarily mean that you'll make money at that same rate. Plus, each job is different. Some patterns go in really quickly, others have a complex pattern to follow. Some jobs require a ton of cutting, others don't.
The first step is knowing what you need to charge to make profit year after year. And I don't just mean what to charge to cover your costs for that job and labor for that job. There are tons of other overhead costs that will incur over the entire year, even the winter, that need to be recovered in our labor rates. So knowing what hourly rate you actually need to make in order to come away with a fair amount of extra money at the end of each year is where you start.
Next is knowing your material costs and knowing how much overage to anticipate. With some pavers we install, we always have to over-order by about 10%. With others, it's closer to 15%. With some tight fitting pavers we might use 1 bag of poly sand for every 120 sq. ft. of patio. But other pavers with larger joints or maybe tumbled pavers might use as much as 1 bag per 50 sq. ft. So knowing your true material costs is really key. Some of this only comes from experience and taking it in the shorts on the first couple jobs until you learn what you did wrong.
Then, the next thing is knowing your production times. And this can only come from experience. When you're just starting doing pavers, you just have to estimate how long you think it's going to take your team to do it. And the end, if you have underbid, you take it in the shorts and learn from that mistake. Then you charge a little more next time, having a little better idea how long the next one is going to take you. Sometimes you overbid and either lose the job or just end up finishing way sooner than you thought. In that case, you may consider adjusting your expected production times down a little, to remain competitive.
A lot of this is learn as you go, my friend. Ain't none of us who can tell you or even have any way of knowing how much YOU need to charge. It's something, unfortunately, you have to learn a lot on your own. By doing a whole lot of them.
Tip - start small. Don't go do large paver jobs right off the bat. Because if you're all wrong on your estimated production times, that can really bite you in the A$$ big time and you an go broke quick. Start by just taking on smaller paver jobs only until you get to know your costs and production times. Then slowly move up to a little larger projects, and on from there.