GLI Pool Products. GLI Pool Products of Youngstown, Ohio, is a privately held swimming pool products manufacturer. The company's core products are pool vinyl liners, pool covers, pool fence and pool cleaners. GLI is committed to delivering our pool products, particularly our custom pool liners and safety covers in under 72 hours. 1. Cheap And Simple Inground Swimming Pool. If you buy one from a professional pool company, an inground swimming pool will easily cost you about $10,000 or more. You can build your own, and one that looks just like it was professionally designed, for less than $3,000. Imagine what you can do with that extra $7,000! This one is really simple.