The folders are complicated because of the folding. They have proprietary features and must be build to high precision. Hinges and clamps increase weight that works against portability. The market is smaller than for regular bikes. With all this, you need to be prepare to spend more than for a regular bike when staying within similar quality expectations. Yes, there will be many circumstances where a budget folder will be easier to handle than a regular bike, but you will not be able to check it in as a regular luggage on a plane and it may be difficult to tackle even on a train. You need to be realistic.