If you're like me, who looks under the rug and on the wash room floor for a dime, hardware prices are always a goblin in the face. I would imagine if you're upgrading on a budget, buy the components one a time, what's on sale first, regular price last, is one strategy.
Usually in a span of 90 days most of your components (at one time or another) will be on sale. I buy stuff like hard drives, ram, cases, hardware coolers and power supplies last because models and types seem have market longevity and only minor upgrades in a 3 year span. Only a sale sparks a immediate buy.
I'm not a geek or a tinkering hobbyist so I keep my hardware for as long as I can. I see upgrades about every 4 to 5 yrs. Heck, I still use a 9 yr. old i7 970 as a dedicated surfing machine. It's expendable if the web punishes it.