UPS Angel: You might just as well ask how long is a piece of string because heliports are as diverse as the surroundings you find them in!
Just take a look at the opening page of the
Heliports Thread to see a representative cross-section of the diversity of facilities out there .. each of them attracting their own unique set of costs.
Even if you specify the number of pads (you mentioned up to six) as well as maintenance and ops/admin accommodation the prices will vary wildly according to the design specs and the location of the facility.
Take a look at the facility in post #1 of the abovementioned thread and compare it with the second photo in post #3 - both have landing spots maintenance and ops/admin accommodation but .. they are constructed according to substantially different design specifications.
In summary; each facility attracts its own set of unique costs according to location and design spec. The location affects the technical requirements involved in construction while the design spec (aside from having to comply with minimum national aviation authority requirements .. and not every operator abides by these) are at the discretion of the developer.