Hi Psi,
Please, plan out a spectrum analyser for 7.5GHz, check on the price of a decent YIG oscillator and the plumbing needed. There is no conspiracy of manufacturers slavering to grab our wallets with their overpriced equipment. The parts cost for a quality specan is very high. Microwave parts are expensive because of the need for precision machining. Look at a microwave parts catalogue, check out the precision connector quality control kit, see the micrometer and precision machined jigs. It needs very high mechanical precision just to make a single connector that will give low VSWR and make measurement possible. Microwave circuits are all ceramics, leadless components, gold and microscope assembly. Nothing cheap there.
If you look up some old HP application notes on spectrum analysers, you'll realise that manufacturers aren't price gouging, it's very expensive the built a specan with a low enough noise floor to be useful. If you read some old manuals, buy an old specan and refurbish the thing, you'll start to understand the requirements and why they cost what they do.
We are very lucky today, even 20 year old solid state gear still works well and is well worth repairing and refurbishing for amateur use. I don't think we've ever had it so good with lots of low cost cheap older test equipment available these days. If you get into the forums that deal with older gear, you'll quickly learn what is really needed to make a usable working instrument. Building one yourself is possible, but hard work. You'll use up heaps of your leisure time. If you find an older piece of gear and refurbish it, you'll be using it at a very reasonable price.
Cheers, Colin
Melbourne