Engagement ring price? 💍🤔

So my boyfriend has been dropping subtle hints about rings recently. Today he asked me how much the average person paid for engagement rings (due to Tebow paying 700k) and then he was asking about how that worked since you have to buy a wedding ring.. after I explained to him, most people just buy a band for the wedding... my boyfriend is financially stable right now, but he’ll be leaving for the marines soon, so I know he would do it sometime soon he would buy a few hundred dollar engagement ring and then when we got married he would purchase a whole new set.. I am in no way materialistic and I’m fine with that completely... I then talked to my mom about the question and she was saying how the cheapest engagement ring she’s been given was 7000... has anyone else got a cheaper one? How much was it if you know? I don’t want him to freak out over prices so I’m trying to find a affordable range to show him on rings I like since he’s asked that as well, so if you want drop pictures of the rings too!