There is no cheap ID
ID is like a project manager , the use different contractors to do different works, eg. hacking, tiling, painting, plumbing, electrical, etc.
In honesty the ID market rate (aka profit) is about 30-50% of the amount you pay. They always have different suppliers eg, tile company, paint company, glass, door, window, flooring who gives rebates for using their product.
If u want to save money you can find you own independant contractors and manage them yourself (using balance payment as a leverage if the workmanship is not good) but its a lot of work and coordination.
You can save abit by purchasing your own materials but again you need to know the job well enough to order enough.
Overall there is no cheap ID,cuz your paying for their time and effort and its their rice bowl.
Only way is to find those not so well known who more hard up for the work and willing to earn lesser. Those well known all stuffed with jobs and they only do it for a certain price (somewhat like your Orchard Hairdresser, but quality is assured most times)
Congrats & Good luck with your new home