Very good recommendations YVR Cockroach but have some thoughts to add.

Banff is also a much larger town and major tourism hub compared to Jasper so it naturally offers more accommodation. To many the appeal of Jasper is it isn't Banff and in Summer isn't as crowded in town and the surrounding national park sights.

There are some good value, quality hotels/motels in Jasper for around $300 with some advance booking which is far less than the ultra-luxury Fairmont hotels which start at CAD$1000/night in Summer without breaking a sweat and not for the top view rooms either so that's quite a bit cheaper to me.

I'll second the suggestion to fly into Vancouver and out of Calgary or vice versa as driving roundtrip is just too far/costly/time consuming but I'll offer a different transportation option between Jasper and Vancouver as Via Rail runs a 23-hour one-way rail journey with sleeper cars. Yes, it's not quite like driving where you can stop for breaks and visit small towns at a leisurely pace but seeing the mountains by rail has a certain romance to it. The one-way Jasper - Vancouver takes you through the mountains during the day so would suggest it over the Vancouver - Jasper route.