Like many PowerSellers I don't believe in making money on postage costs. But based on the theory that 'A Penny Saved is a Penny Earned' there's nothing wrong in seeking ways to cut your delivery costs and add more money to your bank account.
* Cut costs on packing materials. Buy on the local high street and you'll usually pay VAT on top. But if you buy from large office supplier outlets you may get large discounts that counteract the the Value Added Tax. Alternatively, you won’t be charged VAT at all if you buy from non-registered sellers on eBay or buy second hand or liquidated stock at boot sales and flea markets. Buy as much as you can afford, as often as you can, of items you know you'll quickly consume. But don't tie all your money up in packaging so there's no money left to buy stock or pay your eBay fees. Be sensible.
* Learn to pack properly using as little material as possible. But don't cut corners; skimp too much and your package will fall apart or be damaged in the post. Not good for your customer, not good for you, highly damaging for your business, and costly in terms of having to replace product and tackling disgruntled buyers. Oh yes, and managing poor feedback scores!
* Do not forget to change delivery costs in line with increases in postage and packing and other fulfilment costs. Responding to increased postal charges can be a nightmare, especially if you have hundreds of products listed. When postage costs increased recently, my PowerSeller daughter decided to wait, just a while - which in her book means 'never' - until she had time to spare to upgrade all 1,000 of her regular listings. She waited and waited and over several months she ignored a twenty pence price increase. Work 20p out over 400 items a month, over six months. Yes, exactly right, £480, almost £1000 over the year.