。
Can I really buy this at this price?
Literal
Truly this price [at-で] this can-buy-[explanation-んです]-[question-か].
で here marks the price as the circumstance or means of purchase — 'at this price.' で has many such roles: means, location of action, price, manner. 買える is the potential form of 買う. The ~んですか ending politely asks for confirmation with a slightly surprised or curious tone. A natural shopper's exclamation on seeing a bargain.