its £46 or a 100 first class stamps, I send second class or standard parcels add signed for if over £15-20
if selling vouchers etc must be special delivery which is about £5 extra, my Dh and I have sold over 350 items and have had only a couple of not received claims, each was an address fault by purchaser ... one put home postcode on business address another had moved i think 2 completely missing both small value less than £10 so just refunded, ( that is less than 1%) if you send everything signed for even if they paid 99p you may get low DSR for how reasonable were postal charges. I really don't think signed for for everything is necessary
I do think some areas like selling phones or software are more prone to complaints and non arrival than say clothes books and ornaments
for stuff heavier than 1 kg the cheapest way of getting signature is collect+ about £3,99
there is no point in offering first class unless you post the very next day
i think a small mark up on postage is ok for packing I charge about 40p extra for just a bag or envelope 75p for small box and bubblewrap ie china orif a large breakable like coffee set which needs loads of bubble poly chips and double boxing £1.50 extra
if you quote £4 and it costs £2.16 give partial refund as soon as you get home it earns you brownie points and makes you look very honest
if someone buys 3 items make sure combined postage is that; the 3 items individually may have cost £1,72 and you were charging £2 but together they will only cost £3.15 so dont think that charging £5 instead of £6 is doing them a favour its not you shoul charge £4 max still
some people try and use postage to make up for 99p sales