yes, they are the same meaning. 這個杯子怎麼賣means 'what's the price for this the cup'.

這個杯 子多少錢? -> This cup how much? -> How much is this cup? 這個杯子怎麼賣? ->This cup how you sale it? -> How much will you sale this cup? -> How much is this cup?

yes，in this sentence, they have the same meanings.