Well I sure don't think all blades are created equal.
Some points to consider:
Plate thickness - how well will it hold tension? If it warps after a run of cutting and you get runout, all the time spent sanding or puttying bad joints (or replacing frames after they come back because the mitres failed) will long offset the cost.
Brazing of the teeth/quality of the shoulders. Moulding has been known to throw off the cuttoffs. Sometimes the cuttoff hits the teeth. If the brazing or shoulders aren't strong (or the plate is brittle) then replacing teeth/shoulders costs more than the blade.
We require all employees to wear a full facemask when running the table saw after a blade threw a tooth and it struck the saw operator in the forehead (he was wearing safety glasses only.) Blades heat up, brazing fails.
Quality of carbide used in the teeth/number of teeth. If a blade doesn't stay sharp very long then the number of sharpenings will 1) cause more frequent sharping expense 2) cause more wear and then shortened blade life 3) Dull blades heat up causing plate warp and runout, thereby needing hammer and retensioning when sharpening.
A frame is only as good as its mitre. If you make your living building frames, cheap blades are a bad way to go. Ultramitre usually has 2 for one sales at the shows. I know that if I can't make it to a show they have offered me the "show special" over the phone. I am not going to open that can of worms but I have had nothing but excellent results/service from Ultramitre.
As others have said, it may be prudent to buy your blades from someone who is going to also service them. In addition, the hook angle as well as the tooth configuration and quantity of teeth will play a roll in getting good cuts. Cutting a mitre from the top on a pivoting saw is NOT the same as crosscutting (as on a radial saw or sliding table saw) and the blades are usually different.
I have two CTD double mitre saws (air and foot operated) a radial arm saw, a single arm CTD chop saw, a Peterman sliding table saw, and a Delta Unisaw fixed table saw in the shop, plus a Makita compound mitre saw and another Makita chop saw for location work. All have specific blades.
We produce 100's of framed pieces per week and have for 27 years in this shop, so I think we have a bit of experience.