Read around feature film lighting a while back and I would say the following prob applies to gels:
Proper gels are seemingly expensive, but you need to consider why that is before you get annoyed or before deciding to cut costs and go cheap, as the precision involved will be helpful if you get into proper lighting:
- Every batch needs to be precisely consistent in both colour and density and match other batches. Some colours seem to be industry standard even in rival makers, from looking at samples. The same colour names can be found across companies.
- Gels also need to be made of reliable heat resistant material to avoid melting in use (they are given some kind of grading system for heat) and prevent fires breaking out.
- Individual colours and densities have to be ultra precise as they may be used in conjunction with other gels to obtain specific effects. Perhaps one colour on the left, another on the right but where they overlap it becomes 'normal' colour as the opposing colours are colour balanced.
- Its a fairly limited market in that only specialist lighting designers will buy it (TV studios, feature film makers, photographers, stage lighting designers etc) so its probably produced in fairly smallish batches compared to say items of clothing for sale in a high street chain. Size of manufacture runs affect the costs of anything thats made
- Manufacturers have to make a huge range of accurate colours and keep them in stock.
- The manufacturers have to maintain a very high reputation for accuracy, lighting designers and film makers cannot afford to make a multimillion dollar film with expensive actors and technical staff only to find scenes are ruined by colour errors. It could cost them thousands of dollars in a single day and perhaps require re-shoots in addition.
If you want accuracy its more expensive, if you are just messing about experimenting for the first few times or lighting a school play, accuracy matters not so much, so you can buy cheap and not worry about getting any accuracy. Be aware of melting or fire risks though, so keep an eye on cheaper products if you use any lights that produce much heat. Also be aware of fading issues as your colours will change.