I have several things I want to sell but, how much will you buy them for?
1.) I have several things I want to sell but, how much will you buy them for? (売りたいものがいくつかあるけど、いくらなら買う?) 「売りたいもの」は英語でthings I want to sellという表現と訳せます。「いくつか」は英語でseveralと訳せます。「いくらなら買う」は英語でhow much will you buy them forという表現に訳せます。この文書は相手が自分の物を何か買いたい時に使えますが、友達に相談している時は言えません。
友達を相談している時は
I have several things I want to sell but, I don't know for how much people will buy them. (売りたいものがいくつかあるけど、誰かはいくらなら買うのがわからない。)
と言えます。
I have some things I want to sell, but how much are you willing to pay?
I have a couple of things I want to sell but, how much do you want them for?
❶I have some things I want to sell, but how much are you willing to pay?
(売りたいものがいくつかあるけど、いくらなら出せる?)
❷I have a couple of things I want to sell but, how much do you want them for?
(売りたいものがいくつかあるけど、いくらなら買いたい?)
の後に〜 Name your price. (買いたい値段を言って!)。
個人的には❷の言い方が好きです。参考までに!