We were lucky in that neither of ours really asked for anything. We used to talk to them and explain from being very young they can't always have everything and emphasise they are luckier than most etc.
If they'd stropped or got hissy at any time they wouldn't get diddly shit but they didn't. Had a strict rule of tantrums and tears never paying off or being worth their while across the board so that was always a given.
Might be worth working out a deal with your son that he has to do certain jobs to earn pocket money which if he does and manages to save enough you will then put towards the things he really does want. Make him decide and whittle down his list more carefully if he has to work to get what he's after.
I took my daughter to work with me at weekends and school holidays from being 9 or 10yrs old maybe and gave her all the boring jobs to do filing, photocopying, updating files and sorting through mountains of folders.
She loved it and I think what gave her a sense of feeling she was earning her crust was filling out a time-sheet and putting it with everyone else's.
Son used to have certain "jobs" which if he did we'd give him an allowance and a treat him now and then but within reason - can't just buy whatever and whenever.
If he didn't - he didn't get paid and whatever he wanted would just have to wait.
He did keep to his jobs aside from a few lapses but when he got lazy and slacked off, the funds dropped and if it coincided with a new game release he'd have to up the ante and work even harder.
Nephew is generally a kid whose parents never say no or make him go without but when he's at ours, he's put to work and made to muck in and help out and come to the farm / help with the horses and the dogs and he loves it. His parents couldn't believe he'd willingly and happily done all that so I sent photos.
Never any argument or having to bargain it's "OK wellies on you do this and that and then when we're finished we'll go McDonalds"
Just gives a feeling of being grown up and I'm sure it makes the McDonald's taste that bit better when they've earned it 
Work out a fair agreement with him if you can and be a bit cold-hearted if need be in saying he doesn't get things without making some effort and working for them. He doesn't agree to work out an agreement with you he gets nothing at all.
Otherwise he'll have to sharpen up and learn how to compromise and earn his keep.