IMO I've always found, the cheaper cables to be fine. The main difference between the expensive ones is the shielding provided (apparantly). Even if that were the case, you would need a significant amount of Electromagnetic Interference (EMI) for it to actually have any benefit. I usually have a plethora of power (as well as other) cables around my HDMI cable. The fact that data is transmitted digitally means that if interference were to occur, it would alter the digital data and have a similar effect to a bad freeview connection. Digital transmission is basically all or nothing. I'd suggest as others have said, getting an up to date (or recent) version hdmi cable and get it cheap.

I'm glad someone has finally taken the time to debunk this annoying falsehood created by marketing and sales. It's painful to see that people fall into this trap and buy the expensive cables. I can't really blame the sales people as they are given an incentive to help meet their quota set by their employers to sell it. I blame the companies for cashing in on misinformation.

Unless you have several irons, heaters, or vacuum cleaners (or something else that has a huge power usage) practically touching your cable, there shouldn't be a difference (as stated by the OP).