Gaskets are cheap. You can buy them by the 100 from McMaster Carr (lid gaskets come in packs of 10).
If you need to replace posts, it gets a bit pricier and you'd want to consider if it's cost effective at that point to pay whatever they are charging. Poppets are not too bad, but I think posts are about $15 each.
Get universal poppets. 15$ per post sounds high to me but i cant verify since the plac eit hink is cheapest is having web issues. Shop around:) Pin lock posts will be cheaper then ball locks because everyone converts the pinlocks to ball locks now