It would be much cheaper to buy sealsavers if you had to buy materials. I got the material free from work because somebody bought it, threw it away, and I dug it outta the trash.
Same as most of the fancy fucking aerospace bolts and AN fittings on all the stuff I build. As soon as the certs get lost or disassociated from the hardware, it can no longer be used on an aircraft. Voila! Free $150 bolt!