I'd pass.

All of the engineering that goes into the bike plus your weight all meets the pavement at two small patches...where the rubber meets the road.

Skimp on a saddle, headset, bar tape...but don't skimp on a the chain, crankset, rear hub, or tires. If any of the latter fail you might fall.

Good tires cost $50 for a reason. There's a lot of engineering that goes into them.