Brushless motors are not the lowest cost motors on the planet but they are invariably the longest lasting. However, if your project is very price sensitive then a BLDC motor could still be achievable but it is likely that you would save money by using a brushed DC motor. If financial considerations are a major part of your considerations it is worth thinking about the lifespan of the project that you have as a brushless motor controller will last an average 5 times longer than a standard DC motor. If the cost of a brushless system is four times the brushed system but you need solid performance over a long lifespan then it is likely that the brushless motor system will be the most cost effective over the project lifetime.
A useful rule of thumb when selecting a motor for your project is that a brushed DC motor will typically operate well for 2000 hours whereas a brushless DC motor will operate well for 10000 hours. This obviously varies by manufacturer and motor type but if your application is likely to require regular and sustained use then a brushless DC motor and controller could actually be the most cost effective in the long run.